An anaerobic bacterial MsrB model reveals catalytic mechanisms, advantages, and disadvantages provided by selenocysteine and cysteine in reduction of methionine-R-sulfoxide.
We verified and generalized the catalytic features that selenocysteine (Sec) and cysteine (Cys) contribute to the reduction of methionine-R-sulfoxide using an anaerobic bacterial MsrB from Clostridium sp. OhILA as a model protein. The Sec-containing Clostridium MsrB form exhibited 100-fold higher activity than its Cys-containing form, revealing that Sec provided the catalytic advantage of higher activity. However, a resolving Cys was required for the thioredoxin (Trx)-dependent recycling process of the Sec-containing form. Thus, Trx could reduce the selenenylsulfide bond, but its Trx-dependent recycling process was much less efficient compared to that for the disulfide bond in the Cys-containing form, demonstrating an obvious catalytic disadvantage. These data agreed well with our previous data on mammalian MsrBs, and therefore suggested that the catalytic mechanisms, as well as the catalytic advantages and disadvantages provided by the Sec and Cys residues, are most likely conserved from anaerobic bacteria to mammals. Taken together, we propose that the use of Sec in MsrB may depend on a balance between the catalytic advantage of higher activity and the disadvantage of a less efficient regeneration process provided by this residue.
Lee
Tae-Hyung
TH
Department of Biochemistry and Molecular Biology, Yeungnam University College of Medicine, 317-1 Daemyung-dong, Daegu 705-717, Republic of Korea.
Kim
Hwa-Young
HY
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D020134:Catalytic Domain; D002460:Cell Line; D003013:Clostridium / Q000201:enzymology / Q000235:genetics; D003545:Cysteine / Q000737:chemistry; D017931:DNA Primers / Q000235:genetics; D004229:Dithiothreitol / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017279:Selenocysteine / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013879:Thioredoxins / Q000378:metabolism
D001426:Bacterial Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; D017279:Selenocysteine; D013879:Thioredoxins; D008715:Methionine; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D003545:Cysteine; D004229:Dithiothreitol; C013111:methionine sulfoxide