Component A2 of the methylcoenzyme M methylreductase system from Methanobacterium thermoautotrophicum

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Abstract
Component A2 of the methylcoenzyme M methylreductase system of M. thermoautotrophicum was purified 370-fold by liquid chromatography. Homogeneity was obtained by anaerobic preparative polyacrylamide gel electrophoresis. Component A2 is a colorless, air-stable protein consisting of a single polypeptide as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The relative MW of the native protein was determined by high-performance, size exclusion chromatography to be 52,000; on sodium dodecyl sulfate-polyacrylamide gel electrophoresis a value of MW 59,000 was obtained. When cell extract was subjected to N6-ATP-agarose affinity chromatography the methylcoenzyme M methylreductase system was resolved into 2 fractions: 1 of them was component A2. This work provides a new operational definition for component A2, i.e., its characteristic chromatographic behavior on N6-ATP-agarose. However, its functional definition is its ability to reconstitute the methylreductase activity with components A1, A3 and C. Several attempts to assign a role to component A2 are reported.