Learning from hydrogenases: location of a proton pump and of a second FMN in bovine NADH-ubiquinone oxidoreductase (Complex I)

Hydrogenases have clear evolutionary links to the much more complex NADH-ub iquinone oxidoreductases (Complex I). Certain membrane-bound [NiFe]-hydroge nases presumably pump protons. From a detailed comparison of hydrogenases a nd Complex I, it is concluded here that the TYKY subunit in these enzymes i s a special 2[4Fe-4S] ferredoxin, which functions as the electrical driving unit for a proton pump. The comparison further revealed that the flavodoxi n fold from [NiFe]-hydrogenases is presumably conserved in the PSST subunit of Complex I. It is proposed that bovine Complex I and the soluble NAD(+)- reducing hydrogenase from Ralstonia entropha each contain a second FMN grou p. (C) 2000 Federation of European Biochemical Societies. Published by Else vier Science B.V. All rights reserved.