The X-ray structure of the heterodimeric Ni-Fe hydrogenase from Desulf
ovibrio gigas, the enzyme responsible for the metabolism of molecular
hydrogen, has been solved at 2.84 Angstrom resolution. The active site
, which appears to contain, besides nickel, a second metal ion, is bur
ied in the 60K subunit. The 28K subunit, which coordinates one [3Fe-4S
] and two [4Fe-4S] clusters, contains an amino-terminal domain with si
milarities to the redox protein flavodoxin. The structure suggests pla
usible electron and proton transfer pathways.