Reduction Of Methionine Sulfoxide Research Articles

Methionine Sulfoxide Reductase B1 Regulates Hepatocellular Carcinoma Cell Proliferation and Invasion via the Mitogen-Activated Protein Kinase Pathway and Epithelial-Mesenchymal Transition.

Methionine sulfoxide reductase B1 (MsrB1) is a member of the selenoprotein family, which contributes to the reduction of methionine sulfoxides produced from reactive oxygen species (ROS) by redox processes in energy pathways. However, few studies have examined the role of MsrB1 in human hepatocellular carcinoma (HCC). We observed that MsrB1 is highly expressed in HCC tissues and that its expression correlated with the prognoses of patients with HCC after hepatectomy. In vitro, knockdown of MsrB1 inhibits HCC cell growth by MTT and EdU proliferation assay, and MsrB1 interference enhances H2O2/trx-induced apoptosis. We observed that phosphorylation of the key proteins of the MAPK pathway, namely, ERK, MEK, and p53, was inhibited, but PARP and caspase 3 were increased, thus infecting mitochondrial integrity. In vivo, MsrB1 knockdown effectively inhibited tumor growth. Furthermore, MsrB1 knockdown reduced HCC cell migration and invasion in a transwell assay through inhibition of cytoskeletal rearrangement and spread. This change was linked to epithelial-mesenchymal transition (EMT) inhibition resulting from increases in E-cadherin expression and decreases in expression in TGF-β1, Slug, MMP-2/9, and so on. MsrB1 regulates HCC cell proliferation and migration by modulating the MAPK pathway and EMT. Thus, MsrB1 may be a novel therapeutic target with respect to the treatment of HCC.

18 - Myristoylated Methionine Sulfoxide Reductase A Interacts with the Lipid-Binding Protein

Reactive oxygen species (ROS) are produced by a variety of cellular processes including metabolic activity, mitochondria, cellular signaling, and oncogene activity. Methionine sulfoxide reductase A (MsrA) is an antioxidant enzyme that can reduce methionine sulfoxide (MetO) in proteins back to methionine (Met). This enzyme plays a protective role in cells against oxidative damage. Although many proteins with MetO are in vitro substrates of MsrA, no in vivo substrates have been confidently identified. In vitro, MsrA can also function as an oxidase that converts methionine to methionine sulfoxide, but it is also not known if it does so in vivo. The cytosolic form of MsrA is myristoylated, and overexpression of the myristoylated form protects the heart from ischemia-reperfusion injury while overexpression of the non-myristoylated form does not. Here we report a novel binding partner of MsrA, STARD3, identified by use of a human protein microarray. ProtoArray Human Protein Microarray v5.0 contains 9,483 human proteins from multiple protein classes along with 2,016 controls. STARD3 was scored as an interacting protein with high probability. STARD3 contains the star-related lipid transfer (START) domain, and proteins with that domain are implicated in lipid and sterol metabolism. STARD3 is known to bind cholesterol and transport it from the endoplasmic reticulum to the late endosome. We overexpressed both myristoylated MsrA and STARD3 in HEK293 cells and immunoprecipitated cell homogenates with anti-STARD3 antibody. We demonstrated that myristoylated MsrA was co-immunoprecipitated with STARD3, but non-myristoylated form wasn’t. This indicates that myristoylation is required for the interaction. Met307 of STARD3 is known to be essential for lipid binding, and we found that it is also required for the interaction of STARD3 and myristoylated MsrA. Finally, we showed by confocal microscopy that myristoylated MsrA was colocalized with STARD3 at late endosomes/lysosomes. We conclude that myristoylated MsrA binds to STARD3 on the cytoplasmic surface of late endosomes.

Chemistry and Redox Biology of Mycothiol.

Mycothiol (MSH, AcCys-GlcN-Ins) is the main low-molecular weight (LMW) thiol of most Actinomycetes, including the human pathogen Mycobacterium tuberculosis that affects millions of people worldwide. Strains with decreased MSH content show increased susceptibilities to hydroperoxides and electrophilic compounds. In M. tuberculosis, MSH modulates the response to several antituberculosis drugs. Enzymatic routes involving MSH could provide clues for specific drug design. Recent Advances: Physicochemical data argue against a rapid, nonenzymatic reaction of MSH with oxidants, disulfides, or electrophiles. Moreover, exposure of the bacteria to high concentrations of two-electron oxidants resulted in protein mycothiolation. The recently described glutaredoxin-like protein mycoredoxin-1 (Mrx-1) provides a route for catalytic reduction of mycothiolated proteins, protecting critical cysteines from irreversible oxidation. The description of MSH/Mrx-1-dependent activities of peroxidases helped to explain the higher susceptibility to oxidants observed in Actinomycetes lacking MSH. Moreover, the first mycothiol-S-transferase, member of the DinB superfamily of proteins, was described. In Corynebacterium, both the MSH/Mrx-1 and the thioredoxin pathways reduce methionine sulfoxide reductase A. A novel tool for in vivo imaging of the MSH/mycothiol disulfide (MSSM) status allows following changes in the mycothiol redox state during macrophage infection and its relationship with antibiotic sensitivity. Redundancy of MSH with other LMW thiols is starting to be unraveled and could help to rationalize the differences in the reported importance of MSH synthesis observed in vitro versus in animal infection models. Future work should be directed to establish the structural bases of the specificity of MSH-dependent enzymes, thus facilitating drug developments. Antioxid. Redox Signal. 28, 487-504.

Functional comparison of methionine sulphoxide reductase A and B in Corynebacterium glutamicum.

Methionine sulphoxide reductases (Msr) are able to reduce methionine sulfoxide to methionine and protect bacteria against reactive oxygen species (ROS). Many organisms express both methionine sulphoxide reductase A (MsrA), specific for methionine-S-sulfoxide and methionine sulphoxide reductase B (MsrB), active against methionine-R-sulfoxide. Corynebacterium glutamicum expresses MsrA, the function of which has been well defined; however, the function of MsrB has not been studied. Whether MsrB and MsrA play an equally important role in the antioxidant process is also poorly understood. In this study, we identified MsrB encoded by ncgl1823 in C. glutamicum, investigated its function and made a comparison with MsrA. The msrB gene showed a slight effect on utilizing methionine sulfoxide (MetO) as the sole Met source; however, the survival rates showed no sensitivity to oxidants. MsrB showed catalytic activity using thioredoxin/thioredoxin reductase (Trx/TrxR) reducing system as electron donors, but independent from the mycoredoxin 1/mycothione reductase/mycothiol (Mrx1/Mtr/MSH) system. Therefore, MsrB plays a limited role in resisting oxidative stress and it could reduce MetO to Met by the Trx/TrxR reducing system, which is useful for expanding the understanding of the functions of Msr in this important industrial microbe.

221 - STARD3 Interacts with Myristoylated Methionine Sulfoxide Reductase A

Methionine sulfoxide reductase A (MsrA) is a component of the oxidative defense system that reduces methionine sulfoxide (MetO) in proteins back to methionine. Although many proteins with MetO are in vitro substrates of MsrA, no in vivo substrates have been confidently identified. In vitro, MsrA can also function as an oxidase that converts methionine to methionine sulfoxide, but it is also not known if it does so in vivo. The cytosolic form of MsrA is myristoylated, and overexpression of the myristoylated form protects the heart from ischemia-reperfusion injury while overexpression of the non-myristoylated form does not. Previous efforts in our laboratory to identify proteins that interact in vivo with MsrA had not been successful. We now report use of a human protein microarray to identify a protein that binds to MsrA. The ProtoArray Human Protein Microarray v5.0 contains 9,483 human proteins from multiple protein classes along with 2,016 controls. Each protein was expressed as an N-terminal GST- tagged protein and printed in duplicate on the nitrocellulose-coated slide glass. We incubated the slide with biotinylated human MsrA and interrogated the array with streptavidin tagged with Alexa Fluor 647. STARD3 emerged as an interacting protein with a high probability score. We co-expressed MsrA and STARD3 in HEK-293 cells, immunoprecipitated from a homogenate with anti-STARD3, and confirmed that MsrA was co-immunoprecipitated. When non-myristoylated MsrA was co-expressed, no interaction with STARD3 was detected. STARD3 contains the star-related lipid transfer (START) domain, and proteins with that domain have been implicated in lipid and steroid metabolism. STARD3 is known to bind cholesterol and transport it to the late endosome. We conclude that it also binds to myristoylated MsrA, and we are now investigating the physiological significance of the interaction.

Dual sites of protein initiation control the localization and myristoylation of methionine sulfoxide reductase A.

Methionine sulfoxide reductase A is an essential enzyme in the antioxidant system, which scavenges reactive oxygen species through cyclic oxidation and reduction of methionine and methionine sulfoxide. In mammals, one gene encodes two forms of the reductase, one targeted to the cytosol and the other to mitochondria. The cytosolic form displays faster mobility than the mitochondrial form, suggesting a lower molecular weight for the former. The apparent size difference and targeting to two cellular compartments had been proposed to result from differential splicing of mRNA. We now show that differential targeting is effected by use of two initiation sites, one of which includes a mitochondrial targeting sequence, whereas the other does not. We also demonstrate that the mass of the cytosolic form is not less than that of the mitochondrial form; the faster mobility of cytosolic form is due to its myristoylation. Lipidation of methionine sulfoxide reductase A occurs in the mouse, in transfected tissue culture cells, and even in a cell-free protein synthesis system. The physiologic role of myristoylation of MsrA remains to be elucidated.

A Methionine Residue Promotes Hyperoxidation of the Catalytic Cysteine of Mouse Methionine Sulfoxide Reductase A.

Methionine sulfoxide reductase A (msrA) reduces methionine sulfoxide in proteins back to methionine. Its catalytic cysteine (Cys72-SH) has a low pKa that facilitates oxidation by methionine sulfoxide to cysteine sulfenic acid. If the catalytic cycle proceeds efficiently, the sulfenic acid is reduced back to cysteine at the expense of thioredoxin. However, the sulfenic acid is vulnerable to "irreversible" oxidation to cysteine sulfinic acid that inactivates msrA (hyperoxidation). We observed that human msrA is resistant to hyperoxidation while mouse msrA is readily hyperoxidized by micromolar concentrations of hydrogen peroxide. We investigated the basis of this difference in susceptibility to hyperoxidation and established that it is controlled by the presence or absence of a Met residue in the carboxyl-terminal domain of the enzyme, Met229. This residue is Val in human msrA, and when it was mutated to Met, human msrA became sensitive to hyperoxidation. Conversely, mouse msrA was rendered insensitive to hyperoxidation when Met229 was mutated to Val or one of five other residues. Positioning of the methionine at residue 229 is not critical, as hyperoxidation occurred as long as the methionine was located within the group of 14 carboxyl-terminal residues. The carboxyl domain of msrA is known to be flexible and to have access to the active site, and Met residues are known to form stable, noncovalent bonds with aromatic residues through interaction of the sulfur atom with the aromatic ring. We propose that Met229 forms such a bond with Trp74 at the active site, preventing formation of a protective sulfenylamide with Cys72 sulfenic acid. As a consequence, the sulfenic acid is available for facile, irreversible oxidation to cysteine sulfinic acid.

Trypanothion – Wunderwaffe und Achillesferse der Trypanosomatiden

Trypanosomatids are protozoan parasites with a unique trypanothionebased thiol redox metabolism. Mediated by the small oxidoreductase tryparedoxin, trypanothione is the universal electron donor for the biosynthesis of DNA precursors, reduction of methionine sulfoxides as well as detoxification of hydroperoxides by distinct thiol peroxidases. The fact that nearly all enzymes involved are essential renders the pathway attractive for drug development approaches against these parasites.

A dielectric barrier discharge terminally inactivates RNase A by oxidizing sulfur-containing amino acids and breaking structural disulfide bonds

RNases are among the most stable proteins in nature. They even refold spontaneously after heat inactivation, regaining full activity. Due to their stability and universal presence, they often pose a problem when experimenting with RNA. We investigated the capabilities of nonthermal atmospheric-pressure plasmas to inactivate RNase A and studied the inactivation mechanism on a molecular level.While prolonged heating above 90 °C is required for heat inactivating RNase A, direct plasma treatment with a dielectric barrier discharge (DBD) source caused permanent inactivation within minutes. Circular dichroism spectroscopy showed that DBD-treated RNase A unfolds rapidly. Raman spectroscopy indicated methionine modifications and formation of sulfonic acid. A mass spectrometry-based analysis of the protein modifications that occur during plasma treatment over time revealed that methionine sulfoxide formation coincides with protein inactivation. Chemical reduction of methionine sulfoxides partially restored RNase A activity confirming that sulfoxidation is causal and sufficient for RNase A inactivation. Continued plasma exposure led to over-oxidation of structural disulfide bonds. Using antibodies, disulfide bond over-oxidation was shown to be a general protein inactivation mechanism of the DBD. The antibody’s heavy and light chains linked by disulfide bonds dissociated after plasma exposure. Based on their ability to inactivate proteins by oxidation of sulfur-containing amino acids and over-oxidation of disulfide bonds, DBD devices present a viable option for inactivating undesired or hazardous proteins on heat or solvent-sensitive surfaces.

Regulation of protein function by reversible methionine oxidation and the role of selenoprotein MsrB1.

Protein structure and function can be regulated via post-translational modifications by numerous enzymatic and nonenzymatic mechanisms. Regulation involving oxidation of sulfur-containing residues emerged as a key mechanism of redox control. Unraveling the participants and principles of such regulation is necessary for understanding the biological significance of redox control of cellular processes. Reversible oxidation of methionine residues by monooxygenases of the Mical family and subsequent reduction of methionine sulfoxides by a selenocysteine-containing methionine sulfoxide reductase B1 (MsrB1) was found to control the assembly and disassembly of actin in mammals, and the Mical/MsrB pair similarly regulates actin in fruit flies. This finding has opened up new avenues for understanding the use of stereospecific methionine oxidation in regulating cellular processes and the roles of MsrB1 and Micals in regulation of actin dynamics. So far, Micals have been the only known partners of MsrB1, and actin is the only target. It is important to identify additional substrates of Micals and characterize other Mical-like enzymes. Oxidation of methionine, reviewed here, is an emerging but not well-established mechanism. Studies suggest that methionine oxidation is a form of oxidative damage of proteins, a modification that alters protein structure or function, a tool in redox signaling, and a mechanism that controls protein function. Understanding the functional impact of reversible oxidation of methionine will require identification of targets, substrates, and regulators of Micals and Msrs. Linking the biological processes, in which these proteins participate, might also lead to insights into disease conditions, which involve regulation of actin by Micals and Msrs.

Corynebacterium diphtheriae Methionine Sulfoxide Reductase A Exploits a Unique Mycothiol Redox Relay Mechanism

Methionine sulfoxide reductases are conserved enzymes that reduce oxidized methionines in proteins and play a pivotal role in cellular redox signaling. We have unraveled the redox relay mechanisms of methionine sulfoxide reductase A of the pathogen Corynebacterium diphtheriae (Cd-MsrA) and shown that this enzyme is coupled to two independent redox relay pathways. Steady-state kinetics combined with mass spectrometry of Cd-MsrA mutants give a view of the essential cysteine residues for catalysis. Cd-MsrA combines a nucleophilic cysteine sulfenylation reaction with an intramolecular disulfide bond cascade linked to the thioredoxin pathway. Within this cascade, the oxidative equivalents are transferred to the surface of the protein while releasing the reduced substrate. Alternatively, MsrA catalyzes methionine sulfoxide reduction linked to the mycothiol/mycoredoxin-1 pathway. After the nucleophilic cysteine sulfenylation reaction, MsrA forms a mixed disulfide with mycothiol, which is transferred via a thiol disulfide relay mechanism to a second cysteine for reduction by mycoredoxin-1. With x-ray crystallography, we visualize two essential intermediates of the thioredoxin relay mechanism and a cacodylate molecule mimicking the substrate interactions in the active site. The interplay of both redox pathways in redox signaling regulation forms the basis for further research into the oxidative stress response of this pathogen.

A study on the protection of methionine and the reduction of methionine sulfoxide in methionine-containing analogues of the growth-modeling factor Gly-His-Lys

The protection of methionine and the reduction of methionine sulfoxide in methionine-containing analogues of Gly-His-Lys are described. The peptides were synthesized by a solid-phase method using the standard Fmoc procedure. Simultaneous deprotection of the peptide side chain and liberation from the resin were achieved using an appropriate TFA cocktail. The TFA cocktail was selected to minimize oxidation of the methionine residue. The reversible method of methionine oxidation was also studied. Selective identification and quantitative analysis of the methionine-containing peptides are based on an LC–MS study.

Evidence for methionine-sulfoxide-reductase gene transfer from Alphaproteobacteria to the transcriptionally active (macro)nucleus of the ciliate, Euplotes raikovi.

BackgroundDeleterious phenomena of protein oxidation affect every aerobic organism and methionine residues are their elective targets. The reduction of methionine sulfoxides back to methionines is catalyzed by methionine-sulfoxide reductases (Msrs), enzymes which are particularly active in microorganisms because of their unique nature of individual cells directly exposed to environmental oxidation.ResultsFrom the transcriptionally active somatic genome of a common free-living marine protist ciliate, Euplotes raikovi, we cloned multiple gene isoforms encoding Msr of type A (MsrA) committed to repair methionine-S-sulfoxides. One of these isoforms, in addition to including a MsrA-specific nucleotide sequence, included also a sequence specific for a Msr of type B (MsrB) committed to repair methionine-R-sulfoxides. Analyzed for its structural relationships with MsrA and MsrB coding sequences of other organisms, the coding region of this gene (named msrAB) showed much more significant relationships with Msr gene coding sequences of Rhodobacterales and Rhizobiales (Alphaproteobacteria), than of other eukaryotic organisms.ConclusionsBased on the fact that the msrAB gene is delimited by Euplotes-specific regulatory 5′ and 3′ regions and telomeric C4A4/G4T4 repeats, it was concluded that E. raikovi inherited the coding region of this gene through a phenomenon of horizontal gene transfer from species of Alphaproteobacteria with which it coexists in nature and on which it likely feeds.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0288-1) contains supplementary material, which is available to authorized users.

Effect of high hydrostatic pressure on the biosynthesis of sulfur amino acids in Saccharomyces cerevisiae

High hydrostatic pressure (HHP) is successfully applied in several industrial segments, as in vaccine production and food conservation. The response of microorganisms to HHP treatment resemble the responses of other stresses with industrial relevance, like osmotic, temperature and ethanol, which make the HHP a valuable tool in biotechnology research, as in the ethanol production [1]. Amino acids play a key role in central metabolism besides being the building blocks of proteins, and they are important to the HHP stress response. In this study, the Saccharomyces cerevisiae BT0510 was exposed to 50 MPa for 30 min at room temperature, followed by incubation at room pressure with aeration for 15 min. Samples of total RNA were collected every 5 min for transcriptional analysis by DNA microarray technique. Bioinformatics analysis demonstrated the upregulation (≥ 2 fold) by HHP treatment of genes related to the sulfur amino acids synthesis, methionine and cysteine. The HHP treatment induced the genes MET3, MET10, MET14 and MET16, which are correlated with the conversion of intracellular sulfate in sulfide. MET2, related to the conversion of homoserine to O-acetylhomoserine, was also induced by HHP, as well as the gene that codes for Met17p, responsible for the incorporation of sulfide in O-acetylhomoserine to form homocysteine, that will be directed to methionine or cysteine synthesis. These amino acids are directly correlated with sulfur assimilation in yeast cells. Methionine is the S-adenosylmethionine precursor, which participates in the biosynthesis of lipids and polyamines, and is also involved in methylation reactions, being a methyl group donor [2,3]. Cysteine is part of iron-sulfur proteins and is the glutathione biosynthesis precursor. Glutathione maintain the redox state in cytoplasm, therefore, playing an important role in cell response to oxidative stress [2,3]. The key gene related to the biosynthesis of methionine (MET6) was upregulated by HHP, while the gene related to the biosynthesis of cysteine (CYS4) was unaffected. Five minutes after pressure release MET6 was repressed. The genes related to the conversion of methionine to S-adenosylmethionine, SAM1 and SAM2, were downregulated. Methionine residues are important against reactive oxygen species (ROS) [4], and genes associated with the reduction of methionine sulfoxide (MXR1 and MXR2) were induced by HHP treatment, suggesting that methionine plays an important role in the reduction of ROS resulting from stress caused by HHP [5]. Concerning the regulation of sulfur amino acids metabolism, MET28 was strongly induced during the entire HHP and post treatment. Other factors, such as the transcription factor encoded by MET4 were not affected by HHP, and also MET30 that negatively regulates Met4p. Met28p appears to play an important role in the biosynthesis of sulfur amino acids in response to HHP. It seems that this protein participates in the Met4 complexes-DNA stabilization. Methionine biosynthesis upregulation is not related to other stresses, such as heat and osmotic stresses, and appears to be specific to HHP, which reinforces the use of this treatment to study the stress response in microorganisms.

The Insertion Green Monster (iGM) Method for Expression of Multiple Exogenous Genes in Yeast

Being a simple eukaryotic organism, Saccharomyces cerevisiae provides numerous advantages for expression and functional characterization of proteins from higher eukaryotes, including humans. However, studies of complex exogenous pathways using yeast as a host have been hampered by the lack of tools to engineer strains expressing a large number of genetic components. In addition to inserting multiple genes, it is often desirable to knock out or replace multiple endogenous genes that might interfere with the processes studied. Here, we describe the “insertion Green Monster” (iGM) set of expression vectors that enable precise insertion of many heterologous genes into the yeast genome in a rapid and reproducible manner and permit simultaneous replacement of selected yeast genes. As a proof of principle, we have used the iGM method to replace components of the yeast pathway for methionine sulfoxide reduction with genes encoding the human selenoprotein biosynthesis machinery and generated a single yeast strain carrying 11 exogenous components of the selenoprotein biosynthetic pathway in precisely engineered loci.

Dimethyl Sulfide – Significance, Origins, and Control

Dimethyl sulfide (DMS) is a substantial contributor to the aroma of many lager-style beers. Opinion varies on its desirability. It can be derived in beer from two sources: the thermal decomposition of S-methyl-methionine (SMM) produced in the embryo of barley during germination, or the reduction of dimethyl sulfoxide (DMSO, derived from the breakdown of SMM during the curing of malt) by yeast. The enzyme that effects DMSO reduction is a reductase whose primary function is the reduction of methionine sulfoxide and which competes for reducing power with several other cellular systems. Control of DMS production from SMM is achieved by specifying precursor levels in malt, by attending to the vigor and duration of the boil, and by controlling the length of the whirlpool stand. Control of DMS production from yeast is achieved by specifying yeast strain, wort gravity, free amino nitrogen and pH, the type of fermenter (ergo the extent of volatilization), and the fermentation temperature.

A pepper MSRB2 gene confers drought tolerance in rice through the protection of chloroplast-targeted genes.

BackgroundThe perturbation of the steady state of reactive oxygen species (ROS) due to biotic and abiotic stresses in a plant could lead to protein denaturation through the modification of amino acid residues, including the oxidation of methionine residues. Methionine sulfoxide reductases (MSRs) catalyze the reduction of methionine sulfoxide back to the methionine residue. To assess the role of this enzyme, we generated transgenic rice using a pepper CaMSRB2 gene under the control of the rice Rab21 (responsive to ABA protein 21) promoter with/without a selection marker, the bar gene.ResultsA drought resistance test on transgenic plants showed that CaMSRB2 confers drought tolerance to rice, as evidenced by less oxidative stress symptoms and a strengthened PSII quantum yield under stress conditions, and increased survival rate and chlorophyll index after the re-watering. The results from immunoblotting using a methionine sulfoxide antibody and nano-LC-MS/MS spectrometry suggest that porphobilinogen deaminase (PBGD), which is involved in chlorophyll synthesis, is a putative target of CaMSRB2. The oxidized methionine content of PBGD expressed in E. coli increased in the presence of H2O2, and the Met-95 and Met-227 residues of PBGD were reduced by CaMSRB2 in the presence of dithiothreitol (DTT). An expression profiling analysis of the overexpression lines also suggested that photosystems are less severely affected by drought stress.ConclusionsOur results indicate that CaMSRB2 might play an important functional role in chloroplasts for conferring drought stress tolerance in rice.

Characteristics of methionine sulfoxide reductases structure and relationship with neurodegenerative diseases

Methionine can be oxidized to methionine sulfoxide, causing redox imbalance in vivo and inducing many diseases. Methionine sulfoxide reductases (Msrs) can reduce methionine sulfoxide to methionine, thus renovate protein structure and function, and prevent oxidative stress-relevant diseases. This review mainly includes the classification and evolution of Msrs, the protein structural feature and catalytic mechanism, and protein expression via genetic engineering. It summarizes recent development in Msrs and aging or Parkinsons disease or Alzheimers disease, as well as our own results. The prospect of Msrs research is also discussed in this paper.

Physiological mechanism of drought tolerance in transgenic rice plants expressing Capsicum annuum methionine sulfoxide reductase B2 (CaMsrB2) gene

The methionine sulfoxide reductase B2 (MsrB2) gene catalyzes the reduction of free and protein-bound methionine sulfoxide to methionine and is known to provide tolerance to biotic and abiotic environmental stresses. There are yet to be any reports that MsrB2 enhances drought tolerance. Two drought-tolerant transgenic rice lines, L-8 (single copy) and L-23 (two copy), expressing the Capsicum annuum MsrB2 (CaMsrB2) gene were selected for stress tolerance phenotyping under drought stress conditions. CaMsrB2 enhanced relative water content, maintained substantial quantum yield (Fv/Fm ratio), and subsequently improved photosynthetic pigments. Interestingly, L-23, carrying two-copy T-DNA insertion, showed greater drought tolerance through more effective stomatal regulation, carotenoid concentration, and osmotic potential than the wild type. High-tech infrared technology (FLIR SC620) was used for the selection of stress-tolerant physiotypes. Later, the IR results were correlated with other tested physiological parameters. The IR images, average plant temperature, and physiological parameters of the treated plants are discussed in detail.

The Methionine Sulfoxide Reduction System: Selenium Utilization and Methionine Sulfoxide Reductase Enzymes and Their Functions

Selenium is utilized in the methionine sulfoxide reduction system that occurs in most organisms. Methionine sulfoxide reductases (Msrs), MsrA and MsrB, are the enzymes responsible for this system. Msrs repair oxidatively damaged proteins, protect against oxidative stress, and regulate protein function, and have also been implicated in the aging process. Selenoprotein forms of Msrs containing selenocysteine (Sec) at the catalytic site are found in bacteria, algae, and animals. A selenoprotein MsrB1 knockout mouse has been developed. Significant progress in the biochemistry of Msrs has been made, which includes findings of a novel reducing system for Msrs and of an interesting reason for the use of Sec in the Msr system. The effects of mammalian MsrBs, including selenoprotein MsrB1 on fruit fly aging, have been investigated. Furthermore, it is evident that Msrs are involved in methionine metabolism and regulation of the trans-sulfuration pathway. This article presents recent progress in the Msr field while focusing on the physiological roles of mammalian Msrs, functions of selenoprotein forms of Msrs, and their biochemistry. A deeper understanding of the roles of Msrs in redox signaling, the aging process, and metabolism will be achieved. The identity of selenoproteome of Msrs will be sought along with characterization of the identified selenoprotein forms. Exploring new cellular targets and new functions of Msrs is also warranted.