The hydrogenase cytochrome b heme ligands of Azotobacter vinelandii are required for full H(2) oxidation capability.

ABSTRACT: The hydrogenase in Azotobacter vinelandii, like other membrane-bound [NiFe] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. The histidines ligating the hemes in this cytochrome b were identified by H(2) oxidation properties of altered proteins produced by site-directed mutagenesis. Four fully conserved and four partially conserved histidines in HoxZ were substituted with alanine or tyrosine. The roles of these histidines in HoxZ heme binding and hydrogenase were characterized by O(2)-dependent H(2) oxidation and H(2)-dependent methylene blue reduction in vivo. Mutants H33A/Y (H33 replaced by A or Y), H74A/Y, H194A, H208A/Y, and H194,208A lost O(2)-dependent H(2) oxidation activity, H194Y and H136A had partial activity, and H97Y,H98A and H191A had fu

SUBMITTER: Meek L 

PROVIDER: S-EPMC101916 | biostudies-literature | 2000 Jun

REPOSITORIES: biostudies-literature