Structural study of [NiFe]hydrogenase

点击翻译按钮获取中文摘要

Hydrogenases catalyze the reversible oxidation of molecular hydrogen and play a key role in hydrogen metabolism in various bacteria. Hydrogenases are classified into [non-metal], [Fe], [NiFe], and [NiFeSe] hydrogenases according to the metal composition of their active sites. The [NiFe]hydrogenase from D. vulgaris Miyazaki F is composed of a heterodimer with a total molecular mass of 91 kDa. The active site of the [NiFe] hydrogenases in the oxidized form is composed of Ni and Fe atoms with four cysteinyl sulfur and four non-protein ligands (S/O, CO, CN or SO). Carbon monoxide (CO) was known as a reversible inhibitor of hydrogenases. The carbon monoxide complex of [NiFe]hydrogenase from D. v. Miyazaki has been prepared and characterized by X-ray crystallography, and absorption and Raman spectroscopy. The exogenously added CO was found to be bound to the Ni atom at the Ni-Fe active site. Distinct changes were observed in the electron density distribution of the Ni and sγ(Cys546) atoms between the CO-bound and CO-liberated structures for all the crystals tested. One of the CO-bound structures showed an additional electron density peak between the CO and Sγ(Cys546), suggesting that an intermediate of the catalytic reaction was trapped at the active site. The novel structural features found near the Ni and Sγ(Cys546) atoms suggest that these two atoms at the Ni-Fe active site play a key role during the initial process to bind H_2.