Formaldehyde ferredoxin oxidoreductase from Pyrococcus furiosus: The 1.85 angstrom resolution crystal structure and its mechanistic implications

Crystal structures of formaldehyde ferredoxin oxidoreductase (FOR), a tungs topterin-containing protein from the hyperthermophilic archaeon Pyrococcus furiosus, have been determined in the native state and as a complex with th e inhibitor glutarate at 1.85 Angstrom and 2.4 Angstrom resolution, respect ively. The native structure was solved by molecular replacement using the s tructure of the homologous P. furiosus aldehyde ferredoxin oxidoreductase ( AOR) as the initial model. Residues are identified in FOR that may be invol ved in either the catalytic mechanism or in determining substrate specifici ty. The binding site on FOR for the physiological electron acceptor, P. fur iosus ferredoxin (Fd), has been established from an FOR-Fd cocrystal struct ure. Based on the arrangement of redox centers in this structure, an electr on transfer pathway is proposed that begins at the tungsten center, leads t o the (4Fe:4S) cluster of FOR via one of the two pterins that coordinate th e tungsten, and ends at the (4Fe:4S) cluster of ferredoxin. This pathway in cludes two residues that coordinate the (4Fe:4S) clusters, Cys287 of FOR an d Asp14 of ferredoxin. Similarities in the active site structures between F OR and the unrelated molybdoenzyme aldehyde oxidoreductase from Desulfovibr io gigas suggest that both enzymes utilize a common mechanism for aldehyde oxidation. (C) 1999 Academic Press.