Methionine is a highly susceptible amino acid that can be oxidized to S and R diastereomeric forms of methionine sulfoxide by many of the reactive oxygen species generated in biological systems. Methionine sulfoxide r...Methionine is a highly susceptible amino acid that can be oxidized to S and R diastereomeric forms of methionine sulfoxide by many of the reactive oxygen species generated in biological systems. Methionine sulfoxide reductases (Msrs) are thioredoxin-linked enzymes involved in the enzymatic conversion of methionine sulfoxide to methionine. Although MsrA and MsrB have the same function of methionine reduction, they differ in substrate specifi city, active site composition, subcellular localization, and evolution. MsrA has been localized in different ocular regions and is abundantly expressed in the retina and in retinal pigment epithelial (RPE) cells. MsrA protects cells from oxidative stress. Overexpression of MsrA increases resistance to cell death, while silencing or knocking down MsrA decreases cell survival; events that are mediated by mitochondria. MsrA participates in protein-protein interaction with several other cellular proteins. The interaction of MsrAwith α-crystallins is of utmost importance given the known functions of the latter in protein folding, neuroprotection, and cell survival. Oxidation of methionine residues in α-crystallins results in loss of chaperone function and possibly its antiapoptotic properties. Recent work from our laboratory has shown that MsrA is co-localized with αA and αB crystallins in the retinal samples of patients with age-related macular degen- eration. We have also found that chemically induced hypoxia regulates the expression of MsrA and MsrB2 in human RPE cells. Thus, MsrA is a critical enzyme that participates in cell and tissue protection, and its interaction with other proteins/growth factors may provide a target for therapeutic strategies to prevent degenerative diseases.展开更多
Methionine oxidation to methionine sulfoxide （MetSO） is reversed by two types of methionine sulfoxide reducrases （MSRs）, A and B, specific to the S- and R-diastereomers of MetSO, respectively. MSR genes are found ...Methionine oxidation to methionine sulfoxide （MetSO） is reversed by two types of methionine sulfoxide reducrases （MSRs）, A and B, specific to the S- and R-diastereomers of MetSO, respectively. MSR genes are found in most organisms from bacteria to human. In the current review, we first compare the organization of the MSR gene families in photosynthetic organisms from cyanobacteria to higher plants. The analysis reveals that MSRs constitute complex families in higher plants, bryophytes, and algae compared to cyanobacteria and all non-photosynthetic organisms. We also perform a classification, based on gene number and structure, position of redox-active cysteines and predicted sub-cellular localization. The various catalytic mechanisms and potential physiological electron donors involved in the regeneration of MSR activity are then de- scribed. Data available from higher plants reveal that MSRs fulfill an essential physiological function during environmental constraints through a role in protein repair and in protection against oxidative damage. Taking into consideration the ex- pression patterns of MSR genes in plants and the known roles of these genes in non-photosynthetic cells, other functions of MSRs are discussed during specific developmental stages and ageing in photosynthetic organisms.展开更多
Mitochondrial superoxide overproduction is believed to be responsible for the neurotoxicity associated with neurodegeneration.Mitochondria-targeted antioxidants,such as MitoQ,have emerged as potentially effective anti...Mitochondrial superoxide overproduction is believed to be responsible for the neurotoxicity associated with neurodegeneration.Mitochondria-targeted antioxidants,such as MitoQ,have emerged as potentially effective antioxidant therapies.Methionine sulfoxide reductase A(MsrA)is a key mitochondrial-localized endogenous antioxidative enzyme and it can scavenge oxidizing species by catalyzing the methionine(Met)-centered redox cycle(MCRC).In this study,we observed that the natural L-Met acted as a good scavenger for antimycin A-induced mitochondrial superoxide overproduction in PC12 cells.This antioxidation was largely dependent on the Met oxidase activity of MsrA.S-methyl-L-cysteine(SMLC),a natural analogue of Met that is abundantly found in garlic and cabbage,could activate the Met oxidase activity of MsrA to scavenge free radicals.Furthermore,SMLC protected against antimycin A-induced mitochondrial membrane depolarization and alleviated 1-methyl-4-phenylpyridinium(MPP+)-induced neurotoxicity.Thus,our data highlighted the possibility for SMLC supplement in the detoxication of mitochondrial damage by activating the Met oxidase activity of MsrA.展开更多
Oxidation and reduction of some amino acids are one of the molecular mechanisms for regulating the function of proteins. The oxidation of methionine (Met) to methionine sulfoxide (Met(O)) results in decreasing or loss...Oxidation and reduction of some amino acids are one of the molecular mechanisms for regulating the function of proteins. The oxidation of methionine (Met) to methionine sulfoxide (Met(O)) results in decreasing or loss of the biological activity of related proteins. It was found that peptide methionine sulfoxide reductase (msrA) can reduce Met(O) to Met and therefore restored the biological function of the oxidized proteins. To reveal the methionine oxidation-reduction mechanism in human body, in this study, the cDNA sequence of bovine msrA was used as an information-probe to screen the human EST database. Based on a contig assembled from homologous ESTs, a 1 256-bp human MSRA cDNA was cloned from several human cDNA libraries. The cDNA contains an open reading frame (ORF) of 705 bp in length, which encodes 235 amino acid residues. Homology comparison revealed that human MSRA shares 88% and 61% identities with bovine and Escherichia coli msrA protein respectively. Expression pattern analysis revealed a展开更多
基金Supported by Grants from NIH (EY01545, EY03040)The Arnold and Mabel Beckman Foundation (to Hinton DR)a grant to the Department of Ophthalmology by Research to Prevent Blindness
文摘Methionine is a highly susceptible amino acid that can be oxidized to S and R diastereomeric forms of methionine sulfoxide by many of the reactive oxygen species generated in biological systems. Methionine sulfoxide reductases (Msrs) are thioredoxin-linked enzymes involved in the enzymatic conversion of methionine sulfoxide to methionine. Although MsrA and MsrB have the same function of methionine reduction, they differ in substrate specifi city, active site composition, subcellular localization, and evolution. MsrA has been localized in different ocular regions and is abundantly expressed in the retina and in retinal pigment epithelial (RPE) cells. MsrA protects cells from oxidative stress. Overexpression of MsrA increases resistance to cell death, while silencing or knocking down MsrA decreases cell survival; events that are mediated by mitochondria. MsrA participates in protein-protein interaction with several other cellular proteins. The interaction of MsrAwith α-crystallins is of utmost importance given the known functions of the latter in protein folding, neuroprotection, and cell survival. Oxidation of methionine residues in α-crystallins results in loss of chaperone function and possibly its antiapoptotic properties. Recent work from our laboratory has shown that MsrA is co-localized with αA and αB crystallins in the retinal samples of patients with age-related macular degen- eration. We have also found that chemically induced hypoxia regulates the expression of MsrA and MsrB2 in human RPE cells. Thus, MsrA is a critical enzyme that participates in cell and tissue protection, and its interaction with other proteins/growth factors may provide a target for therapeutic strategies to prevent degenerative diseases.
文摘Methionine oxidation to methionine sulfoxide （MetSO） is reversed by two types of methionine sulfoxide reducrases （MSRs）, A and B, specific to the S- and R-diastereomers of MetSO, respectively. MSR genes are found in most organisms from bacteria to human. In the current review, we first compare the organization of the MSR gene families in photosynthetic organisms from cyanobacteria to higher plants. The analysis reveals that MSRs constitute complex families in higher plants, bryophytes, and algae compared to cyanobacteria and all non-photosynthetic organisms. We also perform a classification, based on gene number and structure, position of redox-active cysteines and predicted sub-cellular localization. The various catalytic mechanisms and potential physiological electron donors involved in the regeneration of MSR activity are then de- scribed. Data available from higher plants reveal that MSRs fulfill an essential physiological function during environmental constraints through a role in protein repair and in protection against oxidative damage. Taking into consideration the ex- pression patterns of MSR genes in plants and the known roles of these genes in non-photosynthetic cells, other functions of MSRs are discussed during specific developmental stages and ageing in photosynthetic organisms.
基金This work was supported by grants from the National Natural Science Foundation of China(No.81773712,No.81473198)the Foundation for Innovative Research Groups of NSFC(No.81721005)+2 种基金the National Basic Research Program of China(973 Program,No.2014CB744601)Science Fund for Creative Research Groups of the Natural Science Foundation of Hubei Province(No.2015CFA020)PCSIRT(No.IRT13016).
文摘Mitochondrial superoxide overproduction is believed to be responsible for the neurotoxicity associated with neurodegeneration.Mitochondria-targeted antioxidants,such as MitoQ,have emerged as potentially effective antioxidant therapies.Methionine sulfoxide reductase A(MsrA)is a key mitochondrial-localized endogenous antioxidative enzyme and it can scavenge oxidizing species by catalyzing the methionine(Met)-centered redox cycle(MCRC).In this study,we observed that the natural L-Met acted as a good scavenger for antimycin A-induced mitochondrial superoxide overproduction in PC12 cells.This antioxidation was largely dependent on the Met oxidase activity of MsrA.S-methyl-L-cysteine(SMLC),a natural analogue of Met that is abundantly found in garlic and cabbage,could activate the Met oxidase activity of MsrA to scavenge free radicals.Furthermore,SMLC protected against antimycin A-induced mitochondrial membrane depolarization and alleviated 1-methyl-4-phenylpyridinium(MPP+)-induced neurotoxicity.Thus,our data highlighted the possibility for SMLC supplement in the detoxication of mitochondrial damage by activating the Met oxidase activity of MsrA.
文摘Oxidation and reduction of some amino acids are one of the molecular mechanisms for regulating the function of proteins. The oxidation of methionine (Met) to methionine sulfoxide (Met(O)) results in decreasing or loss of the biological activity of related proteins. It was found that peptide methionine sulfoxide reductase (msrA) can reduce Met(O) to Met and therefore restored the biological function of the oxidized proteins. To reveal the methionine oxidation-reduction mechanism in human body, in this study, the cDNA sequence of bovine msrA was used as an information-probe to screen the human EST database. Based on a contig assembled from homologous ESTs, a 1 256-bp human MSRA cDNA was cloned from several human cDNA libraries. The cDNA contains an open reading frame (ORF) of 705 bp in length, which encodes 235 amino acid residues. Homology comparison revealed that human MSRA shares 88% and 61% identities with bovine and Escherichia coli msrA protein respectively. Expression pattern analysis revealed a
