A selenium-containing hydrogenase from Methanococcus vannielii. Identification of the selenium moiety as a selenocysteine residue.

摘要: A 75Se-labeled hydrogenase was purified to near homogeneity from extracts of Methanococcus vannielii cells grown in the presence [75Se]selenite. The molecular weight enzyme estimated as 340,000 by gel filtration. tends aggregate and occurs also a larger protein species (Mr = 1.3 x 10(6)). same phenomenon observed on native electrophoretic analysis. Hydrogenase activity exhibited these two bands proportional 75Se content. Both reduce natural cofactor, 8-hydroxy-5-deazaflavin, tetrazolium dyes with hydrogen. Sodium dodecyl sulfate-gel electrophoresis showed that is present exclusively an Mr 42,000 subunit. value 3.8 g atoms selenium/mol 340,000) determined atomic absorption chemical form selenium shown be selenocysteine. This identified [75Se]carboxymethyl [75Se]carboxyethyl derivatives acid hydrolysates alkylated protein. extremely oxygen-sensitive but can reactivated incubation hydrogen dithiothreitol.