Recombinant human Selenoprotein R/MSRB1 protein

SEPX1, also known as Methionine sulfoxide reductase B1 (MSRB1), is a selenoprotein. Methionine sulfoxide reductases (MSRs) catalyze reduction of free and protein-bound methionine sulfoxides to corresponding methionines. The oxidation of methionine by ROS generates a diastereomeric mixture of methionine-S-sulfoxide (Met-S-SO) and methionine-R-sulfoxide (Met-R-SO) . Two distinct enzyme families evolved for reduction of these sulfoxides, with methionine-S-sulfoxide reductase (MsrA) being stereospecific for Met-S-SO and methionine-R-sulfoxide reductase (MsrB) for Met-R-SO. In bacteria, the selenocystein (Sec/u) element is located immediately following the uGA codon within the reading frame for the selenoprotein so we mutated Sec-95 to Cys. Recombinant human SEPX1 protein, fused to His-tag at N-terminus, was expressed in E. coli and purified by using conventional chromatography.