Requirement of the nickel tetrapyrrole F430 for in vitro methanogenesis: reconstitution of methylreductase component C from its dissociated subunits.

The subunits and the nickel tetrapyrrole factor F430 of the methylreductase component C from Methanobacterium thermoautotrophicum have been separated from one another and reassociated to form an intact, active enzyme. The individual subunits were extracted from polyacrylamide gels after NaDodSO4/polyacrylamide gel electrophoresis and reassociated with F430 under a H2 atmosphere at 55 degrees C. When these components were reassociated in the presence of the substrate 2-(methylthio)ethanesulfonic acid, 72% of the original activity was recovered. When F430 was omitted, no activity was detected in the reconstituted methylreductase reaction. Individual subunits were inactive, when incubated in the presence of factor F430, 2-(methylthio)ethanesulfonic acid, magnesium acetate, and ATP. Evidence suggests that F430 binds to the large Mr 68,000 subunit of component C.