Studies on the reducing systems for plant and animal thioredoxin-independent methionine sulfoxide reductases B.
Two distinct stereospecific methionine sulfoxide reductases (Msr), MsrA and MsrB reduce the oxidized methionine (Met), methionine sulfoxide [Met(O)], back to Met. In this report, we examined the reducing systems required for the activities of two chloroplastic MsrB enzymes (NtMsrB1 and NtMsrB2) from tobacco (Nicotiana tabacum). We found that NtMrsB1, but not NtMsrB2, could use dithiothreitol as an efficient hydrogen donor. In contrast Escherichia coli thioredoxin (Trx) could serve as a reducing agent for NtMsrB2, but not for NtMsrB1. Similar to previously reported human Trx-independent hMsrB2 and hMsrB3, NtMsrB1 could also use bovine liver thionein and selenocysteamine as reducing agents. Furthermore, the unique plant Trx-like protein CDSP32 was shown to reduce NtMsrB1, hMsrB2 and hMsrB3. All these tested Trx-independent MsrB enzymes lack an additional cysteine (resolving cysteine) that is capable of forming a disulfide bond on the enzyme during the catalytic reaction. Our results indicate that plant and animal MsrB enzymes lacking a resolving cysteine likely share a similar reaction mechanism.
Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA.
Di
D
Ding
Daphna
D
Sagher
Edith
E
Laugier
Pascal
P
Rey
Herbert
H
Weissbach
Xing-Hai
XH
Zhang
D000595:Amino Acid Sequence; D000818:Animals; D002736:Chloroplasts / Q000201:enzymology; D003538:Cystamine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D051150:Methionine Sulfoxide Reductases; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D016566:Organoselenium Compounds / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D020539:Sequence Analysis, Protein; D013379:Substrate Specificity; D013879:Thioredoxins / Q000378:metabolism*; D014026:Nicotiana / Q000201:enzymology; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
D008840:Microfilament Proteins; D016566:Organoselenium Compounds; D010940:Plant Proteins; D014157:Transcription Factors; C014807:selenocystamine; D013879:Thioredoxins; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; C120376:MSRB2 protein, human; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; C524352:MSRB3 protein, human; D003545:Cysteine; D003538:Cystamine