Von Willebrand Factor Receptor Research Articles

THE PLATELET HYPOREACTIVITY OF VERY LOW BIRTH WEIGHT (VLBW) NEONATES IS AGE-DEPENDENT. ▴ 1722

We have previously demonstrated that, as compared to adults, the platelets of VLBW neonates are markedly hyporeactive on day 0 - 1 of life. In this study, we examined the age dependency of this hyporeactivity. On days 0 - 1, 3- 4, and 10 - 14, peripheral blood was collected from 9 stable VLBW neonates(birth weight <1 kg, gestation <29 weeks) and compared to peripheral blood from normal adults run in parallel. To circumvent methodologic problems, we used a whole blood flow cytometric method to examine the activation-dependent increase in platelet surface P-selectin (reflectingα granule secretion) and decrease in platelet surface glycoprotein (GP) Ib (the von Willebrand factor receptor), in response to either thrombin 2 U/mL, U46619 10 μM (a stable thromboxane A2 analogue), or ADP 20μM with epinephrine 20 μM. In addition, we used a whole blood flow cytometric method to examine the activation-dependent generation of procoagulant activity (as reported by a monoclonal antibody to activated coagulation factor V) on platelets and platelet-derived microparticles, in response to either the calcium ionophore A23187 80 μM with CaCl2 3 mM or a combination of thrombin 2 U/mL, collagen 10 μg/mL, and CaCl2 3 mM. On day 0 - 1, VLBW neonatal platelets were less reactive than adult platelets to thrombin, U46619, and ADP/epinephrine, as determined by the extent of increase in platelet surface P-selectin, decrease in platelet surface GPIb, and generation of procoagulant activity. On days 3 - 4, this hyporeactivity was even more marked. However, on day 10 - 14, the platelets of VLBW neonates were almost as reactive as adult platelets. In summary, in the physiologic milieu of whole blood, as determined by the increase in platelet surface P-selectin, decrease in platelet surface GPIb, and generation of procoagulant activity, the platelets of VLBW neonates are maximally hyporeactive (compared to adult platelets) on days 3 - 4, but return to almost the adult range by days 10 - 14. Given that IVH is also maximal on days 3 - 4, these defects may contribute to the propensity of VLBW neonates to IVH.

ChemInform Abstract: Sulfobacins A and B, Novel von Willebrand Factor Receptor Antagonists. Part 1. Production, Isolation, Characterization, and Biological Activities.

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Fate of the GPIb/IX receptor complex following activation of human platelets.

Many excellent workers have concluded that platelet glycoprotein Ib/IX complex, the receptor for von Willebrand factor (vWF) is down-regulated in its ability to bind vWF or monoclonal antibodies and virtually cleared from the exterior surface to internal membranes following exposure of the cells to thrombin in suspension. Studies carried out in our laboratory, however, have not supported the concept of down-regulation or clearance. Experiments employing aggregation-disaggregation-reaggregation, agglutination and flow cytometry have demonstrated that physiologic levels of calcium ions prevent or reverse the phenomenon of down-regulation. GPIb/IX receptors remain edge to edge on surface-activated platelets, whether or not the cells are also exposed to thrombin before or after spreading. Addition of two ligands, fibrinogen labeled gold to mark GPIIb/IIIa and vWF to identify GPIb/IX, to discoid platelets before surface activation demonstrates that GPIIb/IIIa is a mobile receptor that concentrates with its ligand in cell centers while vWF bound to GPIb/IX moves with the membrane as it expands to the lateral edges of spread cell margins. Immunogold studies of thrombin-activated platelets in suspension reveal no clearance of GPIb/IX receptors, bound or not to vWF, from exposed surfaces to internal membranes. The clearance to the OCS reported by others may be due to difficulties encountered in staining GPIb/IX lining OCS channels in resting discoid platelets.

The platelet glycoprotein Ib-V-IX system: regulation of gene expression.

Platelet glycoproteins (GPs) Ib-V-IX form the surface receptor for von Willebrand factor, and this receptor-ligand interaction mediates the shear-dependent adhesion of platelets to damaged arterial vessel walls. The receptor is a multicomponent structure consisting of four distinct polypeptides (heterodimeric GPIb: Ib alpha-Mr143k and Ib beta-Mr22k; GPV-Mr83k; GPIX-Mr20k), and each of the four cDNAs and genes has been cloned and characterized. The genes appear to have evolved from a common progenitor genomic sequence related to that encoding GPIX. They share simple structures with few introns and possess common consensus regulatory sequences (GATA, ets, Sp-1) in their 5' flanks. Both the GPIb alpha and the GPIX promoters have been analyzed by transfection of reporter constructs into hematopoietic and nonhematopoietic cells. The promoters function in a tissue-specific fashion, and gel shift and mutational analyses indicate that GATA and ets sequences regulate activity. In the case of the GPIX promoter, footprints confirm the role of the ets-related consensus region. Recent studies of GPIb beta transcriptional regulation suggest that an aberrant polyadenylation signal, located in the 3' end of the gene immediately upstream of the GPIb beta gene, allows in vitro expression of a rare extended fusion transcript encoding both the upstream protein and GPIb beta. Little detailed information is available in regard to expression of the GPV gene. In summary, the genes of the GPIb-V-IX system display features of other megakaryocyte/platelet genes, but the unique regulatory events that direct the selective expression of these genes in megakaryocytes remain to be defined.

A Point Mutation in Glycoprotein IX Coding Sequence (Cys73(TGT) to Tyr(TAT)) Causes Impaired Surface Expression of GPIb/IX/V Complex in Two Families with Bernard-Souiier Syndrome

Bernard-Soulier syndrome (BSS) is a rare inherited bleeding disorder which is caused by abnormal expression or function of the glycoprotein (GP) Ib/IX/V complex, a platelet major receptor for von Willebrand factor. We studied four BSS patients in two unrelated families in which the same and novel mutation was found. Flow cytometric analysis showed that GPIX was completely absent but residual amounts of GPIb alpha and GPV were detectable in these patients. We analyzed all coding regions of GPIb alpha, GPIb beta, GPV and GPIX which were amplified from the patients' genomic DNA by the polymerase chain reaction (PCR). In all four cases, we identified a point mutation in the GPIX coding region that changes the codon for cysteine 73 (TGT) to a codon for tyrosine (TAT). Furthermore, we confirmed by a transient expression study that the mutation caused the loss of adequate surface expression of GPIX. Since cysteine might be important for the secondary structure, this mutation of GPIX gene would lead to a dramatic conformational change of GPIX protein, resulting in the reduced surface expression. We concluded that this novel point mutation of the GPIX gene was responsible for BSS in these families.

Thrombin-induced inhibition of platelet agglutination by von Willebrand factor (vWF): reversal by ionized calcium

The present study has used washed human platelets combined with ethylene diamine tetracetic acid (EDTA) to determine the influence of calcium ions on thrombin-induced down-regulation of glycoprotein (GP) Ib/IX, the platelet surface receptor for von Willebrand factor (vWF). Bovine plasma vWF (BvWF) does not require the antibiotic, ristocetin, or calcium ions to cause agglutination of platelets. Thus, EDTA platelets agglutinate as well with BvWF as platelets in the absence of the chelating agent. Thrombin treatment of EDTA platelets prevented subsequent agglutination by BvWF. However, the addition of calcium ions to the sample restores sensitivity of the six PIb/IX receptors, and irreversible agglutination occurs when BvWF is added. Monoclonal antibodies to GPIb/IX and GPIIb/IIIa demonstrated that restoration of refractory platelet sensitivity to BvWF was related to GPIb/IX, not to GPIIb/IIIa. Experimental results suggest that GPIb/IX receptors on thrombin-treated EDTA platelets can be down-regulated by thrombin, but are not cleared from the surface to internal membranes.

Functional Expression of Single Chain Glycoprotein lb Alpha on the Surface of COS Cells and BHK Cells

The GpIb-IX complex constitutes the major receptor for von Willebrand factor (vWF) on the surface of blood platelets. The vWF-binding site has been mapped to one of the three constituent chains, GpIb alpha. Surface expression of GpIb alpha depends on the correct intracellular assembly with the GpIb beta and GpIX chains. We have now grafted a portion of the extracellular domain of GpIb alpha containing the vWF binding site onto the transmembrane/intracellular domain of the single chain surface molecule ICAM-1. Transient transfection of this chimeric protein in COS cells resulted in surface expression as assessed by immunostaining of live cells. Similar results were obtained after stable transfection into BHK cells. Purified vWF bound to the surface of transfected cells in the presence of ristocetin and botrocetin with a Kd of 52 ng/ml, comparable to the Kd for fixed platelets (65.5 ng/ml). This study indicates that functional expression of the vWF-binding domain of GpIb alpha on the surface of mammalian cells can be obtained in the absence of GpIb beta and GpIX. Furthermore, this model system simplifies existing methods for the assessment of the functional consequences of mutations in GpIb alpha as found in pseudo-von Willebrand disease and Bernard-Soulier syndrome.

Differentiation of the two forms of GPIb functioning as receptors for alpha-thrombin and von Willebrand factor: Ca2+ responses of protease-treated human platelets activated with alpha-thrombin and the tethered ligand peptide.

Previous results have shown that both GPIb and the seven transmembrane domain receptor (STDR) are required for optimal thrombin-induced platelet activation (Greco et al., 1996). Limited degradation (approximately 10%) of GPIb and the STDR by elastase reduced the Ca2+ response to 0.5 nM alpha-thrombin by only 10% whereas Serratia marcescens metalloprotease reduced the Ca2+ response by 80% and fully abrogated high-affinity thrombin binding and aggregation. vWF/ristocetin-induced agglutination was only slightly reduced (20%) while Ca2+ and aggregation response to higher thrombin concentrations were retained. At increasing elastase and Serratia protease concentrations, degradation of the STDR proceeded from the amino-terminal domain, but Ca2+ responses to the tethered ligand peptide SFLLRNPNDKYEPF were not affected by either protease. These results show that both putative thrombin receptors are susceptible to protease degradation and suggest that Serratia protease is able to differentiate the GPIb-mediated events associated with thrombin activation from those associated with ristocetin-induced agglutination.

Thioesterification of platelet proteins with saturated and polyunsaturated fatty acids.

We have demonstrated that more than 20 platelet proteins can be acylated with fatty acids via thioester linkages. These include the glycoprotein IX beta chain of glycoprotein Ib, components of the von Willebrand factor receptor on the platelet surface, P-selectin, and alpha subunits of Gz, Gq, and Gi. Our studies have shown that platelet proteins can be posttranslationally acylated in thioester linkages not only with palmitate but with myristate and also with the eicosanoid precursor fatty acids arachidonate and eicosapentaenoate. Thioesterification of platelet proteins with fatty acids other than palmitate may have significant functional consequences for reversible binding of proteins to membranes.

Mocarhagin, a novel cobra venom metalloproteinase, cleaves the platelet von Willebrand factor receptor glycoprotein Ibalpha. Identification of the sulfated tyrosine/anionic sequence Tyr-276-Glu-282 of glycoprotein Ibalpha as a binding site for von Willebrand factor and alpha-thrombin.

Platelet adhesion to the subendothelium is the initiating event in hemostasis and thrombosis and involves the binding of von Willebrand factor (vWF) by the platelet membrane glycoprotein (GP) Ib-IX complex. The alpha-chain of GP Ib contains binding sites for both vWF and alpha-thrombin within a 45-kDa N-terminal tryptic fragment. In the present study, we have further delineated these sites using smaller proteolytic fragments and functional antibodies. Mocarhagin, a cobra venom metallaproteinase, generates the fragment His-1-Glu-282, while cathepsin G, a neutrophil granule serine protease, generates a slightly smaller fragment, His-1-Leu-275. His-1-Glu-282 was as effective as intact soluble GP Ibalpha (glycocalicin) in inhibiting botrocetin-dependent binding of vWF to washed platelets (IC50 approximately 0.3 microM) whereas His-1-Leu-275 was an order of magnitude less effective (IC50 approximately 3 microM). Residues Tyr-276-Glu-282 (YDYYPEE) are part of an anionic region homologous to thrombin-binding molecules such as hirudin. In ligand blot analysis, thrombin blotted the His-1-Glu-282 fragment, but not His-1-Leu-275. The three tyrosine residues within Tyr-276-Glu-282 meet the consensus criteria for O-sulfation. A method was developed to distinguish O-sulfated from nonsulfated tyrosine residues based on differences in the UV absorbance spectra. Residues Tyr-276-Glu-282 were isolated from glycocalicin by proteolysis with mocarhagin and cathepsin G. Ion spray mass spectrometry confirmed that Tyr-278 and Tyr-279 was only approximately 50% O-sulfated. Four anti-GP Ibalpha monoclonal antibodies (SZ2, ES85, C34 and VM16d) were found to be modulator-specific, strongly inhibiting botrocetin-dependent binding of vWF, but having less or no effect on ristocetin-dependent vWF binding. These antibodies also inhibited the binding of thrombin to fixed platelets. Immunoprecipitation with GP ibalpha fragments defined the epitopes for these antibodies as SZ2 (Tyr-276-Glu-282), ES85 (Asp-283-Arg-293), C34 (His-1-Glu-282), and VM16d (His-1-Leu-275). An antibody which inhibited ristocetin-dependent, as well as botrocetin-dependent, vWF binding but had no effect on thrombin binding (Ak2) had an epitope within His-1-Leu-275. These findings indicate that the sulfated tyrosine/anionic GP Ibalpha residues Tyr-276-Glu-282 are important for the binding of thrombin and botrocetin-dependent binding of thrombin and the botrocetin-dependent binding of vWF, but that vWF also interacts with residues within His-1-Leu-275.

The Genetic Defect in Two Well-Studied Cases of Bernard-Soulier Syndrome: A Point Mutation in the Fifth Leucine-Rich Repeat of Platelet Glycoprotein Iba

Bernard-Soulier syndrome (B-Ss) is a rare congenital bleeding disorder caused by abnormal giant platelets, thrombocytopenia, and defective glycoprotein (GP) Ib-V-IX, the adhesion receptor for von Willebrand factor (vWF). This report describes the molecular defect in two related individuals with well-established B-Ss whose platelets exhibit decreased GPIb-IX and normal GPV on their surfaces. The GPIb-V-IX genes of the two patients were analyzed by Southern blotting, hetero-duplex analysis, and polymerase chain reaction (PCR) amplification/sequencing. A point mutation was found in codon 129 of the GPIb alpha gene that results in the substitution of proline for leucine in the first position of the fifth leucine-rich glycoprotein repeat of the mature gene product. The mutation (CTC: leucine, wild-type to CCC: proline, mutant) eliminates a Sac I restriction site, facilitating analysis of the mutation in the propositi (both homozygotes), unaffected family members (8 heterozygotes and 8 wild-type), and 58 normal controls (116 wild-type alleles). The status of the genomes was confirmed by the sequencing of platelet cDNA. The mutation does not affect transcription of the Ib-IX genes, as estimated by PCR and Northern blot analysis, but it does inhibit surface expression of the receptor as assessed by transient transfection of mutant and wild-type GPIb alpha genes into mouse Ib beta-IX L cells. Many of the cells (43%) transfected with the normal gene express surface GPIb alpha, whereas untransfected cells and those transfected with the mutant gene lack surface GPIb alpha entirely. Patient platelets were tested both for vWF binding in the presence of ristocetin and for surface GPIb-IX expression. In these instances, despite their inability to agglutinate with ristocetin and vWF, patient platelets exhibit about 40% of normal vWF binding and 40% of normal Ib-IX surface antigens. The results suggest that the described mutation (GPIb alpha: Leu129 -> Pro) affects the conformation of the GPIb-V-IX receptor, alters its availability on platelet surfaces, and causes the observed Bernard-Soulier phenotype.

Retention of Glycoprotein Ib/IX Receptors on External Surfaces of Thrombin-Activated Platelets in Suspension

The present study has evaluated the hypothesis stating that glycoprotein (GP) Ib/IX, the receptor for von Willebrand factor (vWF), is downregulated and cleared from exposed surfaces to channels of the open canalicular system (OCS) on platelets activated by thrombin in suspension. Cryosections of resting and thrombin-activated platelets fixed at intervals of 1 to 30 minutes after stimulation by thrombin and stained with antiglycocalicin antibody and protein A gold showed no decrease in the density of GPIb/IX receptors on the platelet surface or increase on linings of the OCS at any interval after stimulation by thrombin. Thin sections of platelets exposed to thrombin in suspension followed by settling onto a plastic chamber for intervals of 1 to 30 minutes revealed retention of GPIb/IX receptors on exposed surfaces detected by vWF, anti-vWF, and protein A gold throughout the 30-minute period of study. Results of this investigation indicate that GPIb/IX receptors remain on the surface of platelets activated by thrombin in suspension, are not cleared to the OCS, and retain the ability to bind vWF for at least 30 minutes.

Management of the Thrombocytopenic Cardiac Surgical Patient???A Role for Aprotinin?

The use of aprotinin in this setting can be justified on a number of grounds. Van Oeveren et al.2 showed that aprotinin prevents decrease in the platelet receptor for von Willebrand factor, which mediates platelet adhesion to endothelial cells during cardiopulmonary bypass (CPB). In addition, aprotinin inhibits the hyperfibrinolysis associated with CPB. This hyperfibrinolysis may be of particular concern in the thrombocytopenic patient, as platelet-derived plasmino-gen-activator inhibitor is particularly critical to protecting the clot from plasmin-induced lysis. Indeed, platelet-rich clots are notoriously more difficult than platelet-poor clots for the cardiologist to lyse with fibrinolytic therapy. Thus, treatment of the thrombocytopenic cardiac surgical patient with an inhibitor of fibrinolysis is a sound strategy and, as in this case, may significantly contribute to a better outcome.

Interaction of Platelet Glycoprotein V with Glycoprotein Ib-IX Regulates Expression of the Glycoproteins and Binding of von Willebrand Factor to Glycoprotein Ib-IX in Transfected Cells

The goal of the present study was to determine whether platelet glycoprotein (GP) V interacts directly with the von Willebrand factor receptor GP Ib-IX and, if so, whether it affects the expression and function of this receptor. A melanoma cell line that does not contain actin-binding protein was transfected with the cDNAs coding for GP V and for each of the three subunits of GP Ib-IX. GP V co-immunoprecipitated and co-localized with GP Ib-IX. Although GP V could be expressed in the absence of GP Ib-IX, the amount incorporated in the membrane was markedly increased when GP Ib-IX was present. Similarly, there was an enhanced expression of GP Ib-IX on the cell surface in the presence of GP V. The binding affinity of botrocetin-induced von Willebrand factor to GP Ib-IX was unaffected by the presence or absence of GP V. However, the binding capacity was increased by the presence of GP V. We conclude that GP V interacts directly with GP Ib-IX, that GP V must associate with GP Ib-IX to be efficiently expressed in the membrane, and that GP V increases the binding capacity of the cells for von Willebrand factor by enhancing the surface expression of the GP Ib-IX complex.

Substitution of Val for Met at Residue 239 of Platelet Glycoprotein Ibα in Japanese Patients With Platelet-Type von Willebrand Disease

Genomic DNA was studied from four patients with platelet-type von Willebrand disease (vWD) from two Japanese families previously reported. The entire coding region of platelet glycoprotein (GP) Ib alpha, a component of the platelet receptor for von Willebrand factor (vWF), was examined by polymerase chain reaction (PCR) followed by direct DNA sequence analysis. A single point mutation was found in all patients resulting in substitution of Val (GTG) for Met (ATG) at residue 239 of GPIb alpha. All patients were heterozygous for the mutation, whereas none of the unaffected family members had an amino acid substitution at residue 239. Because the nucleotide substitution destroys an NIa III restriction site on GPIb alpha, PCR products were subjected to digestion with this enzyme; DNA fragments from both normal and mutant alleles were detected in all affected individuals. In allele-specific PCR, DNA was amplified from patients' genomic DNA using either adenine- or guanine-containing primers, whereas only adenine-containing primer successfully amplified DNA from normal individuals. Cloning of amplified DNA into bacteriophage M13mp19 and subsequent DNA sequence analysis confirmed the mutation in these families. The absence of the amino acid substitution at residue 239 of GPIb alpha in the normal individuals tested, together with the linkage of this substitution to the phenotypic expression of disease in these two families and in a family recently described suggest that this amino acid change is a molecular basis for platelet-type vWD, and the substitution may produce a quite similar phenotype to the one reported previously (Gly to Val at residue 233 of GPIb alpha).

Effects of Dietary Manipulation with Fish Oil on Platelet Receptors for von Willebrand Factor and Fibrinogen in Patients with End-Stage Renal Disease

Effects of Dietary Manipulation with Fish Oil on Platelet Receptors for von Willebrand Factor and Fibrinogen in Patients with End-Stage Renal Disease

Antithrombotic Effect of a Recombinant von Willebrand Factor, VCL, on Nitrogen Laser-Induced Thrombus Formation in Guinea Pig Mesenteric Arteries

To assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded. In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i.v. injection inhibits risocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time.(ABSTRACT TRUNCATED AT 250 WORDS)

Sulfobacins A and B, novel von Willebrand factor receptor antagonists. I. Production, isolation, characterization and biological activities.

Sulfobacins A and B, novel von Willebrand factor (vWF) receptor antagonists, have been isolated from the culture broth of Chryseobacterium sp. (Flavobacterium sp.) NR 2993 by ethyl acetate extraction, and by Sephadex LH-20 and silica gel column chromatographies. The physico-chemical properties of the sulfobacins indicate that their structures are completely different from that of aurintricarboxylic acid, the one known vWF receptor antagonist. Sulfobacins A and B inhibit the binding of vWF to its receptor with IC50S of 0.47 and 2.2 microM, respectively. Sulfobacin A also inhibits ristocetin-induced agglutination in human platelets fixed with paraformaldehyde with an IC50 of 0.58 microM.

Growth and metastasis of human breast cancers in athymic nude mice.

To evaluate critically the merit of utilizing a wound model for growing human tumors, a series of increasingly difficult human tumor types were tested for growth at sites of trauma in athymic nude mice. In vitro tumor lines as well as fresh tumors from the breast, colon, rectum, lung, and a metastasis from an unknown primary were intraperitoneally injected into mice subjected to intra-abdominal organ injury. Successful xenografts were obtained from nine of 10 cell lines and 14 of 24 fresh tumors. The latter included five of six (83%) colon cancers, one lung tumor, metastatic tumor of unknown primary, three of four (75%) metastatic breast cancers and four of six (67%) estrogen receptor (ER)-negative breast primary tumors. Six ER-positive breast tumors tested failed to grow in mice without estrogen supplementation. Xenografts from two breast, two colon and the lung cancers formed spontaneous metastases and all xenografts tested were able to yield serial transplants in the surgical wound model. Histologically, all xenografts and their metastases were identical to their respective donor tumors. Transplantability in mice without exogenous estrogen supplementation was linked to the absence of estrogen and progesterone receptors in breast tumors. Transplantability of the cell lines was associated with the expression of cell surface receptors for fibronectin and hyaluronic acid. Receptors for other extracellular matrix components, namely, laminin, vitronectin, collagen, fibrinogen or von Willebrand factor were not associated with transplantability. These results demonstrate that a large proportion of human tumors, including the breast tumors, can be successfully xenografted into athymic mice by providing them with a healing wound environment, and that such xenografts grown at ectopic sites exhibit metastatic ability.

Sulfobacins A and B, novel von Willebrand factor receptor antagonists. II. Structural elucidation.

Sulfobacins A and B are novel von Willebrand factor (vWF) receptor antagonists produced by Chryseobacterium sp. NR 2993. The structures of sulfobacins A and B have been determined to be (2R,3R)-3-hydroxy-2-[(R)-3-hydroxy-15-methylhexadecanamido]-15- methylhexadecanesulfonic acid and (2R,3R)-3-hydroxy-15-methyl-2-[13-methyltetradecanamido]- hexadecanesulfonic acid, respectively, by various 2D NMR experiments and by methanolysis. The absolute configurations of the sulfobacins were determined by a modified MOSHER's method. The structures are related to sulfonolipids, major components of the cell envelope of gliding bacteria of the genus Cytophaga.