Structural studies on hydrogenase maturation protein HypE

Department of Life Science, University of Hyogo, Graduate School of Life Science
â—‹Yasuhito Shomura Yoshiki Higuchi

Hydrogenases are essential proteins in most microorganisms. The enzymes catalyze reversible oxidation of molecular hydrogen into protons and electrons. The members can be divided into a few classes according to the metal content of the active site. [NiFe] hydrogenases, a class of the members, are characterized by the [NiFe] cluster and the synthesis of the dimetallic center involves the products of at least six genes, hyp (hydrogenase pleiotropic genes) A, B, C, D, E and F. Of these, HypE and HypF are required for the synthesis of cyanide, one of the non-protein ligand for the iron, with using carbamoylphosphate as a substrate. Cyanide is known to be highly toxic to most of the organisms and the complexity of the dimetallic center implies the involvement of the sophisticated mechanism catalyzed by the HypE-HypF machinery. HypF first transfers carbamoyl moiety from carbamoylphosphate to the C-terminal cysteine in HypE, and subsequently, the carbamoyl residue is decarboxylated into thiocyanate per se. It is now open as to how ATP hydrolyses (both HypE and F have ATPase activity) are coupled to the reactions and whether the two enzymes cooperatively catalyze the reaction or not. To this end, we solved the crystal structure of HypE. The detail of the atomic structure and the proposed mechanism of the ATP-dependent dehydration reaction will be reported.