Function of ech hydrogenase in ferredoxin-dependent, membrane-bound electron transport in methanosarcina mazei

Reduced ferredoxin is an intermediate in the methylotrophic and aceticlastie pathway of methanogenesis and donates electrons to membrane-integral proteins, which transfer electrons to the heterodisulfide reductase. A ferredoxin interaction has been observed previously for the Ech hydrogenase. Here we present a detailed analysis of a Methanosarcina mazei [DELTA]ech mutant which shows decreased ferredoxin-dependent membrane-bound electron transport activity, a lower growth rate, and faster substrate consumption. Evidence is presented that a second protein whose identity is unknown oxidizes reduced ferredoxin, indicating an involvement in methanogenesis from methylated [C.sub.1] compounds. doi: 10.1128/JB.01307-09