SDR Family Research Articles

Glucose reintroduction triggers the activation of Nrf2 during experimental ischemia reperfusion

Reperfusion results in a rapid reintroduction of oxygen, glucose, and other restricted components to an ischemic tissue. It brings with it not only the necessary components for cell survival but also a burst of oxidative stress and cellular damage. In this study, our primary aims were to investigate glucose as a determining factor for the activation of the transcription factor NF-E2-related factor 2 (Nrf2) upon reperfusion and the expression of downstream anti-oxidant NADPH-dependent reductases. Exposure of renal epithelial HK-2 cells to oxygen and glucose reintroduction after depletion resulted in an increase in nuclear translocation of Nrf2 protein in a manner dependent upon glucose. This activation and the induction of the Nrf2-dependent gene NAD(P)H dehydrogenase, quinone 1 (NQO1) was observed to be maximum at a concentration of 5 mM glucose. Microarray analysis of mRNA from siRNA targeted cells under these conditions revealed the Nrf2-dependent expression of NADPH-dependent reductase enzymes NQO1, Aldo-keto reductase family 1, members C1-3 and dehydrogenase/reductase (SDR family) member 2 (DHRS2), all genes demonstrated to protect against oxidative stress-mediated cellular injury. In addition, NQO1 and DHRS2 mRNA levels were specifically upregulated on glucose reintroduction and were also increased in an in vivo ischemia reperfusion injury model of murine renal pedicle clamping. In conclusion, we demonstrate that glucose reintroduction after depletion activates Nrf2 and Nrf2 regulated NADPH-dependent reductase expression. We suggest these findings represent a previously unreported mechanism for the activation of Nrf2 as a cytoprotective pathway in IRI.

Association of Gene-Gene Interactions with Venous Thromboembolism (VTE): A Merged/Imputed Genome-Wide Scan/Candidate-Gene Case-Control Study

Abstract 1242 Background:While bivariate interactions between Factor V Leiden, prothrombin G20201A and hereditary deficiency of antithrombin, protein C and protein S compound VTE risk, whether other gene-gene interactions are associated with VTE is largely unknown. Objective:To test novel gene-gene interactions for an association with VTE. Methods:Genome-wide scan (Illumina 660Q [557,112 SNPs]) and candidate gene (12,551 SNPs in 764 genes within the anticoagulant, procoagulant, fibrinolytic and innate immunity pathways) genotypes from 1270 non-Hispanic adults of European ancestry with objectively-diagnosed VTE (cases; no cancer, venous catheter or antiphospholipid antibodies) and 1302 controls (frequency-matched on case age, gender, race, MI/stroke status) were merged and imputed to about 2.5 million SNPs with MACH using HapMap Phase 2 (60 CEU). We tested all pairwise SNP-SNP interactions using a 2-stage procedure (fast epistasis in the first stage and age, gender, MI/stroke status and state of residence adjusted analysis using logistic regression in the second stage). Results:The mean ± standard deviation case and control ages were 54.4 ± 16.2 and 55.6 ± 15.8 years, respectively and 51% were female. Among 2.299×10^12 pairwise interactions tested, 900 million reached a p-value<E-06 and were be tested in the second stage. Of these, 2417, 278 and 22 SNP-SNP interactions reached p-values ≤1E-9, 1E–10, and1E-11 respectively; 121 SNP-SNP interactions reached the Bonferroni statistical significance threshold (≤5.555659E-11). The gene-gene pairwise interactions with p-values≤1E-11 were: (1) chromosome 3 open reading frame 70 (C3orf70) – short-chain dehydrogenase/reductase (SDR family) member 4 (DHRS4), (2) 1-acylglycerol-3-phosphate O-acyltransferase 4 (AGPAT4) - NIMA (never in mitosis gene a)-related kinase 6 (NEK6), and (3) TatD DNase domain containing 2 (TATDN2) – WAS protein family, member 3 (WASF3). No gene function data are available for C3orf70. DHRS4 encodes for a 3-ketosteroid reductase important for active steroid hormone regulation, AGPAT4 is important for signal transduction and lipid biosynthesis, NEK6 encodes for Nek6 which downregulates p53-induced cancer cell senescence, TATDN2 encodes a deoxyribonuclease, WASF3 encodes for a member of the Wiskott-Aldrich syndrome protein family which are key regulators of signal transduction and cytoskeletal reorganization in hematopoietic cells. Conclusion:Pairwise gene-gene interaction analyses suggest potential associations between VTE and novel genes for future testing in replication studies. Disclosures:Heit:Daiichi Sankyo: Consultancy, Honoraria.

Inhibition of Transcription Factor Specificity Protein 1 Alters the Gene Expression Profile of Keratinocytes Leading to Upregulation of Kallikrein-Related Peptidases and Thymic Stromal Lymphopoietin

Transcription factor specificity protein 1 (Sp1) is involved in diverse cellular functions. We recently found that Sp1 was significantly decreased in skin biopsies from patients with atopic dermatitis (AD) and had an even greater reduction in AD patients with a history of eczema herpeticum. In the current study, we sought to better understand the role of Sp1 in skin biological processes by using a small interfering RNA (siRNA) technique to knock down Sp1 gene expression in normal human keratinocytes (NHK) and investigated the genome-wide gene expression profiling of Sp1- silenced NHK. The gene arrays revealed that 53 genes had more than three-fold changes in expression in Sp1-silenced NHK as compared to scrambled siRNA silenced cells. Strikingly, six kallikrein-related peptidase genes, KLK5, KLK6, KLK7, KLK8, KLK10, and KLK12 were up-regulated in NHK following Sp1 silencing. Functionally, protease activity was significantly enhanced in Sp1-silenced keratinocytes as compared to scrambled siRNA silenced keratinocytes. Moreover, thymic stromal lymphopoietin (TSLP), an epithelial derived TH2 promoting cytokine, was induced in Sp1-silenced keratinocytes due to elevated kallikrein activity. These results indicate that Sp1 expression deficiency leads to abnormally increased kallikrein protease activity in keratinocytes and may contribute to TH2 immune responses in the skin by inducing TSLP.

Biochemical Studies and Ligand-bound Structures of Biphenyl Dehydrogenase from Pandoraea pnomenusa Strain B-356 Reveal a Basis for Broad Specificity of the Enzyme

Biphenyl dehydrogenase, a member of short-chain dehydrogenase/reductase enzymes, catalyzes the second step of the biphenyl/polychlorinated biphenyls catabolic pathway in bacteria. To understand the molecular basis for the broad substrate specificity of Pandoraea pnomenusa strain B-356 biphenyl dehydrogenase (BphB(B-356)), the crystal structures of the apo-enzyme, the binary complex with NAD(+), and the ternary complexes with NAD(+)-2,3-dihydroxybiphenyl and NAD(+)-4,4'-dihydroxybiphenyl were determined at 2.2-, 2.5-, 2.4-, and 2.1-Å resolutions, respectively. A crystal structure representing an intermediate state of the enzyme was also obtained in which the substrate binding loop was ordered as compared with the apo and binary forms but it was displaced significantly with respect to the ternary structures. These five structures reveal that the substrate binding loop is highly mobile and that its conformation changes during ligand binding, starting from a disorganized loop in the apo state to a well organized loop structure in the ligand-bound form. Conformational changes are induced during ligand binding; forming a well defined cavity to accommodate a wide variety of substrates. This explains the biochemical data that shows BphB(B-356) converts the dihydrodiol metabolites of 3,3'-dichlorobiphenyl, 2,4,4'-trichlorobiphenyl, and 2,6-dichlorobiphenyl to their respective dihydroxy metabolites. For the first time, a combination of structural, biochemical, and molecular docking studies of BphB(B-356) elucidate the unique ability of the enzyme to transform the cis-dihydrodiols of double meta-, para-, and ortho-substituted chlorobiphenyls.

Sequence Diversities of Serine-Aspartate Repeat Genes among Staphylococcus aureus Isolates from Different Hosts Presumably by Horizontal Gene Transfer

BackgroundHorizontal gene transfer (HGT) is recognized as one of the major forces for bacterial genome evolution. Many clinically important bacteria may acquire virulence factors and antibiotic resistance through HGT. The comparative genomic analysis has become an important tool for identifying HGT in emerging pathogens. In this study, the Serine-Aspartate Repeat (Sdr) family has been compared among different sources of Staphylococcus aureus (S. aureus) to discover sequence diversities within their genomes.Methodology/Principal FindingsFour sdr genes were analyzed for 21 different S. aureus strains and 218 mastitis-associated S. aureus isolates from Canada. Comparative genomic analyses revealed that S. aureus strains from bovine mastitis (RF122 and mastitis isolates in this study), ovine mastitis (ED133), pig (ST398), chicken (ED98), and human methicillin-resistant S. aureus (MRSA) (TCH130, MRSA252, Mu3, Mu50, N315, 04-02981, JH1 and JH9) were highly associated with one another, presumably due to HGT. In addition, several types of insertion and deletion were found in sdr genes of many isolates. A new insertion sequence was found in mastitis isolates, which was presumably responsible for the HGT of sdrC gene among different strains. Moreover, the sdr genes could be used to type S. aureus. Regional difference of sdr genes distribution was also indicated among the tested S. aureus isolates. Finally, certain associations were found between sdr genes and subclinical or clinical mastitis isolates.ConclusionsCertain sdr gene sequences were shared in S. aureus strains and isolates from different species presumably due to HGT. Our results also suggest that the distributional assay of virulence factors should detect the full sequences or full functional regions of these factors. The traditional assay using short conserved regions may not be accurate or credible. These findings have important implications with regard to animal husbandry practices that may inadvertently enhance the contact of human and animal bacterial pathogens.

Effect of Imids on Gene Expression Profiles of Fresh Human Myeloma Cells

AbstractAbstract 5013Immunomodulatory drugs represent a major therapeutic advance in the treatment of patients with multiple myeloma. While these agents appear to exert various effects on the microenvironment, including effect on immune cells and angiogenesis, a direct effect on the tumor cells themselves is also likely. To describe and compare the effect of the three clinically available agents (thalidomide, lenalidomide, pomalidomide) we analyzed the gene expression profiles of fresh human myeloma cells exposed to thalidomide, lenalidomide or pomalidomide, using high density DNA arrays. Fresh human myeloma samples were obtained from bone marrow aspirates of patients with myeloma, and myeloma cells were immunopurified using anti CD138 magnetic beads. Purified myeloma cells (1.106 cells/ml) were incubated for 24 hours in RPMI 1640 medium supplemented with 10% fetal calf serum under each of the four following conditions: 1) DMSO; 2) thalidomide 40 microM; 3) lenalidomide 1 microM; 4) pomalidomide 100 nM. These levels are achievable in the plasma of MM pts. Pangenomic array experiments were performed usingWhole Human Genome 4 × 44K Agilent one-color microarrays. Data were normalized using the quantile normalization method. Samples were analysed for differentially expressed genes, taking into account both the level of significance and the fold-change. Ten evaluable samples were processed. Exposure to thalidomide, lenalidomide and pomalidomide induced differential expression of 36, 50 and 75 genes, respectively, in comparison to DMSO-exposed controls, the total list including 101 genes. Twelve of these were found to be differentially expressed after exposure to all of the three agents, including trophoblast glycoprotein, WAS protein family member 1, dickkopf homolog 1, pentraxin-related gene, CD28, interleukin 12B, tissue factor pathway inhibitor 2, phospholipase A2, dehydrogenase/reductase (SDR family) member 9, hypothetical LOC145788 and betacellulin. These commonly altered genes could be mechanistically involved in themultiple activities of these agents in multiple myeloma or may represent epiphenoma mechanistically unrelated to drug-induced cell death. Genes differentially expressed between the treatment with each of these agents could be indicative of the different and non-overlapping actions these agents have in multiple myeloma. An example of this is the recent demonstration that pomalidomide is clinically active in lenalidomide refractory patients. These results suggest that exposure to IMIDs induce various intracellular signalization pathways in myeloma cells which might be involved in the cytotoxic activity of these compounds. Disclosures:Dumontet:Celgene: Research Funding.

Where Do Adult Leydig Cells Come From?1

Where Do Adult Leydig Cells Come From?1

A new cotton SDR family gene encodes a polypeptide possessing aldehyde reductase and 3-ketoacyl-CoA reductase activities

To understand regulatory mechanisms of cotton fiber development, microarray analysis has been performed for upland cotton (Gossypium hirsutum). Based on this, a cDNA (GhKCR3) encoding a polypeptide belonging to short-chain alcohol dehydrogenase/reductase family was isolated and cloned. It contains an open reading frame of 987 bp encoding a polypeptide of 328 amino acid residues. Following its overexpression in bacterial cells, the purified recombinant protein specifically uses NADPH to reduce a variety of short-chain aldehydes. A fragment between Gly180 and Gly191 was found to be essential for its catalytic activity. Though the GhKCR3 gene shares low sequence similarities to the ortholog of Saccharomyces cerevisiae YBR159w that encodes 3-ketoacyl-CoA reductase (KCR) catalyzing the second step of fatty acid elongation, it was surprisingly able to complement the yeast ybr159wDelta mutant. Gas chromatography-mass spectrometry analysis showed that very long-chain fatty acids, especially C26:0, were produced in the ybr159wDelta mutant cells expressing GhKCR3. Applying palmitoyl-CoA and malonyl-CoA as substrates, GhKCR3 showed KCR activity in vitro. Quantitative real time-PCR analysis indicated GhKCR3 transcripts accumulated in rapidly elongating fibers, roots, and stems. Our results suggest that GhKCR3 is probably a novel KCR contributing to very long-chain fatty acid biosynthesis in plants.

The structures ofAlcaligenes faecalisD-3-hydroxybutyrate dehydrogenase before and after NAD+and acetate binding suggest a dynamical reaction mechanism as a member of the SDR family

D-3-Hydroxybutyrate dehydrogenase, which catalyzes the reversible reaction between D-3-hydroxybutyrate and acetoacetate, has been classified into the short-chain dehydrogenase/reductase family and is a useful marker in the assay of diabetes mellitus and/or ketoacidosis. The enzyme from Alcaligenes faecalis was crystallized in the apo form and in the holo form with acetate as a substrate analogue. The crystal structures of both forms were determined at 2.2 angstroms resolution. The enzyme is a tetramer composed of four subunits assembled with noncrystallographic 222 point symmetry. Each subunit has two domains. The principal domain adopts the Rossmann fold essential for nucleotide binding, which is a common feature of the SDR family. NAD+ is bound in a large cleft in the domain. The pyrophosphate group of NAD+ is covered by the small additional domain, which is supported by two extended arms allowing domain movement. In the catalytic site, a water molecule is trapped by the catalytic Tyr155 and Ser142 residues in the vicinity of the bound NAD+ and acetate. The substrate analogue acetate is bound above the nicotinamide plane. A substrate (D-3-hydroxybutylate) bound model can reasonably be constructed by adding two C atoms into the void space between the water O atom and the methyl group of the acetate, suggesting a substrate-bound state before enzymatic reaction occurs. Based on these structural features, a reaction mechanism has been proposed.

SdrF, a Staphylococcus epidermidis Surface Protein, Binds Type I Collagen

Staphylococcus epidermidis is the leading cause of device-related infections. These infections require an initial colonization step in which S. epidermidis adheres to the implanted material. This process is usually mediated by specific bacterial surface proteins and host factors coating the foreign device. Some of these surface proteins belong to the serine-aspartate repeat (Sdr) family, which includes adhesins from Staphyloccus aureus and S. epidermidis. Using a heterologous expression system in Lactococcus lactis to overcome possible staphylococcal adherence redundancy we observed that one of these Sdr proteins, SdrF, mediates binding to type I collagen when present on the lactococcal cell surface. We used lactococcal recombinant strains, a protein-protein interaction assay and Western ligand blot analysis to demonstrate that this process occurs via the B domain of SdrF and both the alpha1 and alpha2 chains of type I collagen. It was also found that a single B domain repeat of S. epidermidis 9491 retains the capacity to bind to type I collagen. We demonstrated that the putative ligand binding N-terminal A domain does not bind to collagen which suggests that SdrF might be a multiligand adhesin. Antibodies directed against the B domain significantly reduce in vitro adherence of S. epidermidis to immobilized collagen.

Structure of zinc-independent sorbitol dehydrogenase fromRhodobacter sphaeroidesat 2.4 Å resolution

Recombinant sorbitol dehydrogenase (SDH) from Rhodobacter sphaeroides has been crystallized in the absence of the cofactor NAD(H) and its structure determined to 2.4 A resolution using molecular replacement (refined R and R free factors of 18.8 and 23.8%, respectively). As expected from the sequence and shown by the conserved fold, SDH can be assigned to the short-chain dehydrogenase/reductase protein family. The cofactor NAD and the substrate sorbitol have been modelled into the structure and the active-site architecture, which displays the highly conserved catalytic tetrad of Asn-Ser-Tyr-Lys residues, is discussed in relation to the enzyme mechanism. This is the first structure of a bacterial SDH belonging to the SDR family.

SdrX, a Serine-Aspartate Repeat Protein Expressed by Staphylococcus capitis with Collagen VI Binding Activity

Staphylococcus capitis (S. capitis) has been implicated in a large proportion of coagulase-negative staphylococcal infections in very-low-birth-weight infants. To identify potential therapeutic targets, the S. capitis genome was probed for the presence of genes encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMM). By using Southern blot analysis, an S. capitis gene, designated sdrX, that contained sequence motifs consistent with the Sdr family of MSCRAMM proteins was identified. By using monospecific antisera in Western blot and flow cytometry, SdrX was demonstrated to be expressed on the surface of S. capitis. Human collagen type VI was found to bind both the recombinant A domain of SdrX and viable S. capitis expressing SdrX. SdrX is the first collagen-binding Sdr protein described and is the first MSCRAMM protein identified in S. capitis.

Structure and mechanism of a bacterial haloalcohol dehalogenase: a new variation of the short-chain dehydrogenase/reductase fold without an NAD(P)H binding site.

Haloalcohol dehalogenases are bacterial enzymes that catalyze the cofactor-independent dehalogenation of vicinal haloalcohols such as the genotoxic environmental pollutant 1,3-dichloro-2-propanol, thereby producing an epoxide, a chloride ion and a proton. Here we present X-ray structures of the haloalcohol dehalogenase HheC from Agrobacterium radiobacter AD1, and complexes of the enzyme with an epoxide product and chloride ion, and with a bound haloalcohol substrate mimic. These structures support a catalytic mechanism in which Tyr145 of a Ser-Tyr-Arg catalytic triad deprotonates the haloalcohol hydroxyl function to generate an intramolecular nucleophile that substitutes the vicinal halogen. Haloalcohol dehalogenases are related to the widespread family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDR family), which use a similar Ser-Tyr-Lys/Arg catalytic triad to catalyze reductive or oxidative conversions of various secondary alcohols and ketones. Our results reveal the first structural details of an SDR-related enzyme that catalyzes a substitutive dehalogenation reaction rather than a redox reaction, in which a halide-binding site is found at the location of the NAD(P)H binding site. Structure-based sequence analysis reveals that the various haloalcohol dehalogenases have likely originated from at least two different NAD-binding SDR precursors.

Directed evolution approach to a structural genomics project: Rv2002 from Mycobacterium tuberculosis.

One of the serious bottlenecks in structural genomics projects is overexpression of the target proteins in soluble form. We have applied the directed evolution technique and prepared soluble mutants of the Mycobacterium tuberculosis Rv2002 gene product, the wild type of which had been expressed as inclusion bodies in Escherichia coli. A triple mutant I6TV47MT69K (Rv2002-M3) was chosen for structural and functional characterizations. Enzymatic assays indicate that the Rv2002-M3 protein has a high catalytic activity as a NADH-dependent 3alpha, 20beta-hydroxysteroid dehydrogenase. We have determined the crystal structures of a binary complex with NAD(+) and a ternary complex with androsterone and NADH. The structure reveals that Asp-38 determines the cofactor specificity. The catalytic site includes the triad Ser-140Tyr-153Lys-157. Additionally, it has an unusual feature, Glu-142. Enzymatic assays of the E142A mutant of Rv2002-M3 indicate that Glu-142 reverses the effect of Lys-157 in influencing the pKa of Tyr-153. This study suggests that the Rv2002 gene product is a unique member of the SDR family and is likely to be involved in steroid metabolism in M. tuberculosis. Our work demonstrates the power of the directed evolution technique as a general way of overcoming the difficulties in overexpressing the target proteins in soluble form.

Human type 10 17β-hydroxysteroid dehydrogenase: molecular modelling and substrate docking

17β-hydroxysteroid dehydrogenases catalyze the oxidoreduction of hydroxy/oxo groups at position C17 of steroid hormones, thereby constituting a prereceptor control mechanism of hormone action. At present, 11 different mammalian 17β-hydroxysteroid dehydrogenases have been identified, catalyzing the cell- and steroid-specific activation and inactivation of estrogens and androgens. The human type 10 17β-hydroxysteroid dehydrogenase (17β-HSD-10) is a multifunctional mitochondrial enzyme that efficiently catalyzes the oxidative inactivation at C17 of androgens and estrogens. However, it also mediates oxidation of 3α-hydroxy groups of androgens, thereby reactivating androgen metabolites. Finally, it is involved in β-oxidation of fatty acids by catalyzing the L-hydroxyacyl CoA dehydrogenase reaction of the β-oxidation cycle. These features and expression profiles suggest a critical role of 17β-HSD-10 in neurodegenerative and steroid-dependent cancer forms. Since no three-dimensional structure of 17β-HSD-10 is available, homology modelling was carried out to understand the molecular basis of these substrate specificities. The structure obtained displays the properties of a one-domain, α/β fold enzyme of the SDR family. The active site is located within a large, hydrophobic cleft, which forms optimal contacts with the different steroid surfaces. The data provide explanations for the substrate specificities toward the various classes of sex steroid hormones. The model is suitable to explore substrate and inhibitor characteristics that may be used in the development of novel strategies in the treatment of degenerative or malignant diseases.

Mechanistic roles of Thr134, Tyr160, and Lys 164 in the reaction catalyzed by dTDP-glucose 4,6-dehydratase.

Escherichia coli dTDP-glucose 4,6-dehydratase and UDP-galactose 4-epimerase are members of the short-chain dehydrogenase/reductase SDR family. A highly conserved triad consisting of Ser/Thr, Tyr, and Lys is present in the active sites of these enzymes as well in other SDR proteins. Ser124, Tyr149, and Lys153 in the active site of UDP-galactose 4-epimerase are located in similar positions as the corresponding Thr134, Tyr160, and Lys164, in the active site of dTDP-glucose 4,6-dehydratase. The role of these residues in the first hydride transfer step of the dTDP-glucose 4,6-dehydratase mechanism has been studied by mutagenesis and steady-state kinetic analysis. In all mutants except T134S, the k(cat) values are more than 2 orders of magnitude lower than of wild-type enzyme. The substrate analogue, dTDP-xylose, was used to investigate the effects of the mutations on rate of the first hydride transfer step. The first step becomes significantly rate limiting upon mutation of Tyr160 to Phe and only partly rate limiting in the reaction catalyzed by K164M and T134A dehydratases. The pH dependence of k(cat), the steady-state NADH level, and the fraction of NADH formed with saturating dTDP-xylose show shifts in the pK(a) assigned to Tyr160 to more basic values by mutation of Lys164 and Thr134. The pK(a) of Tyr160, as determined by the pH dependence of NADH formation by dTDP-xylose, is 6.41. Lys164 and Thr134 are believed to play important roles in the stabilization of the anion of Tyr160 in a fashion similar to the roles of the corresponding residues in UDP-galactose 4-epimerase, which facilitate the ionization of Tyr149 in that enzyme [Liu, Y., et al. (1997) Biochemistry 35, 10675--10684]. Tyr160 is presumably the base for the first hydride transfer step, while Thr134 may relay a proton from the sugar to Tyr160.

Searching for the physiological function of 17β-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus: studies of substrate specificity and expression analysis

17β-hydroxysteroid dehydrogenase from the filamentous fungus Cochliobolus lunatus (17β-HSDcl) has recently been characterized. Since its function is still unclear, we performed substrate specificity studies to obtain some indications about its physiological function. Different steroids were studied as putative substrates of recombinant 17β-HSDcl, androgens and estrogens, brassinosteroids, and the fungal steroid herbarulid. Among these androgens and estrogens were most efficiently converted. The following substrates in decreasing order were best reduced: 4-estrene-3,17-dione, 5α-androstane-3,17-dione, 4-androstene-3,17-dione and estrone. Two typical inhibitors were tested: carbenoxolone — a representative inhibitor of the SDR family and quercetin — a diagnostic inhibitor of carbonyl reductases. Among these two quercetin was more efficient. Expression studies revealed that 17β-HSDcl is mainly expressed in the stationary phase of growth indicating its possible involvement in secondary metabolism.

A bone sialoprotein-binding protein from Staphylococcus aureus: a member of the staphylococcal Sdr family

Staphylococcus aureus bacteria, isolated from bone and joint infections, specifically interact with bone sialoprotein (BSP), a glycoprotein of bone and dentine extracellular matrix, via a cell-surface protein of Mr 97000 [Yacoub, Lindahl, Rubin, Wendel, Heinegård and Rydén, (1994) Eur. J. Biochem. 222, 919-925]. Amino acid sequences of seven trypsin fragments from the 97000-Mr BSP-binding protein were determined. A gene encoding a protein encompassing all seven peptide sequences was identified from chromosomal DNA isolated from S. aureus strain O24. This gene encodes a protein with 1171 amino acids, called BSP-binding protein (Bbp), which displays similarity to recently described proteins of the Sdr family from S. aureus. SdrC, SdrD and SdrE encode putative cell-surface proteins with no described ligand specificity. Bbp also shows similarity to a fibrinogen-binding protein from S. epidermidis called Fbe. A serine-aspartic acid repeat sequence was found close to the cell-wall-anchoring Leu-Pro-Xaa-Thr-Gly sequence in the C-terminal end of the protein. Escherichia coli cells were transformed with an expression vector containing a major part of the bbp gene fused to the gene for glutathione S-transferase. The affinity-purified fusion protein bound radiolabelled native BSP, and inhibited the binding of radiolabelled BSP to staphylococcal cells. Serum from patients suffering from bone and joint infection contained antibodies that reacted with the fusion protein of the BSP-binding protein, indicating that the protein is expressed during an infection and is immunogenic. The S. aureus Bbp protein may be important in the localization of bacteria to bone tissue, and thus might be of relevance in the pathogenicity of osteomyelitis.

A bone sialoprotein-binding protein from Staphylococcus aureus: a member of the staphylococcal Sdr family

Staphylococcus aureus bacteria, isolated from bone and joint infections, specifically interact with bone sialoprotein (BSP), a glycoprotein of bone and dentine extracellular matrix, via a cell-surface protein of M(r) 97000 [Yacoub, Lindahl, Rubin, Wendel, Heinegârd and Rydén, (1994) Eur. J. Biochem. 222, 919-925]. Amino acid sequences of seven trypsin fragments from the 97000-M(r) BSP-binding protein were determined. A gene encoding a protein encompassing all seven peptide sequences was identified from chromosomal DNA isolated from S. aureus strain O24. This gene encodes a protein with 1171 amino acids, called BSP-binding protein (Bbp), which displays similarity to recently described proteins of the Sdr family from S. aureus. SdrC, SdrD and SdrE encode putative cell-surface proteins with no described ligand specificity. Bbp also shows similarity to a fibrinogen-binding protein from S. epidermidis called Fbe. A serine-aspartic acid repeat sequence was found close to the cell-wall-anchoring Leu-Pro-Xaa-Thr-Gly sequence in the C-terminal end of the protein. Escherichia coli cells were transformed with an expression vector containing a major part of the bbp gene fused to the gene for glutathione S-transferase. The affinity-purified fusion protein bound radiolabelled native BSP, and inhibited the binding of radiolabelled BSP to staphylococcal cells. Serum from patients suffering from bone and joint infection contained antibodies that reacted with the fusion protein of the BSP-binding protein, indicating that the protein is expressed during an infection and is immunogenic. The S. aureus Bbp protein may be important in the localization of bacteria to bone tissue, and thus might be of relevance in the pathogenicity of osteomyelitis.

The Binding of Calcium to the B-repeat Segment of SdrD, a Cell Surface Protein of Staphylococcus aureus

In the Sdr family of Staphylococcus aureus cell surface proteins, three recently cloned members (Josefsson, E., McCrea, K., Ni Eidhin, D., O'Connell, D., Cox, J. A., Hook, M., and Foster, T. (1998) Microbiology, in press) display variable numbers of B-repeats, i.e. segments of 110-113 residues that probably make up one folding unit. Each B-repeat contains one conserved EF-hand motif and two acidic stretches. Equilibrium dialysis revealed that segment B1-B5 of SrdD contains 14 Ca2+-binding sites with high affinity ([Ca2+]0.5, 4 microM), whereas flow dialysis yielded 5 sites of high affinity (class I) and 10 of low affinity (class II). The discrepancy could be explained by the slow induction of high affinity in the class II sites. Kinetic experiments using fluorescent Ca2+ indicators corroborated slow binding of Ca2+ at the latter sites. Circular dichroism and Trp fluorescence showed that, whereas the Ca2+ form is well folded, the metal-free form seems strongly disorganized. The Ca2+-induced conformational changes comprise both fast and slow steps, giving thus a structural support for the induction of class II Ca2+-binding sites. The B-repeats may act as rulers or springs that modulate the distance between the interactive A region and the bacterial cell surface.