Etienne Frantzy, Spector Daniel, Brot Nathan, Weissbach Herbert
Center for Molecular Biology and Biotechnology, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA.
Biochem Biophys Res Commun. 2003 Jan 10;300(2):378-82. doi: 10.1016/s0006-291x(02)02870-x.
It is known that Escherichia coli methionine mutants can grow on both enantiomers of methionine sulfoxide (met(o)), i.e., met-R-(o) or met-S-(o), indicating the presence of enzymes in E. coli that can reduce each of these enantiomers to methionine (met). Previous studies have identified two members of the methionine sulfoxide reductase (Msr) family of enzymes, MsrA and fSMsr, that could reduce free met-S-(o), but the reduction of free met-R-(o) to met has not been elucidated. One possible candidate is MsrB which is known to reduce met-R-(o) in proteins to met. However, free met-R-(o) is a very poor substrate for MsrB and the level of MsrB activity in E. coli extracts is very low. A new member of the Msr family (fRMsr) has been identified in E. coli extracts that reduces free met-R-(o) to met. Partial purification of FRMsr has been obtained using extracts from an MsrA/MsrB double mutant of E. coli.
已知大肠杆菌甲硫氨酸突变体能够在甲硫氨酸亚砜（met(o)）的两种对映体上生长，即met-R-(o)或met-S-(o)，这表明大肠杆菌中存在能够将这些对映体中的每一种还原为甲硫氨酸（met）的酶。先前的研究已经鉴定出甲硫氨酸亚砜还原酶（Msr）家族的两种酶，MsrA和fSMsr，它们能够还原游离的met-S-(o)，但游离的met-R-(o)还原为met的过程尚未阐明。一种可能的候选酶是MsrB，已知它能将蛋白质中的met-R-(o)还原为met。然而，游离的met-R-(o)是MsrB的一种非常差的底物，并且大肠杆菌提取物中MsrB的活性水平非常低。在大肠杆菌提取物中已鉴定出Msr家族的一个新成员（fRMsr），它能将游离的met-R-(o)还原为met。使用大肠杆菌MsrA/MsrB双突变体的提取物已获得fRMsr的部分纯化产物。
