Expression, purification and crystallization of HybA in Hyb-type [NiFe]-hydrogenase

Hyb-type [NiFe]-hydrogenase (HYB) is encoded in the hyb operon (hybGFEDCBAO). HYB has been considered to be expressed as a complex of four components, HybO (small subunit of hydrogenase unit), HybC (large subunit of hydrogenase unit), HybA (iron-sulfur protein) and HybB (transmembrane protein) in cells. The hydrogenase unit (HybOC) catalyzes the decomposition and production of molecular H2. The physiological function of HYB has not been established yet, but presumed to supply electrons derived from H2 to the final quinone pool in the anaerobic metabolism of glycerol with fumarate. HybA is considered to play a role to link the hydrogenase activity and the quinone reduction1. The crystal structure of the hydrogenase unit of HYB (HybOC) was already determined, and the molecular mechanism of the stability against O2 was proposed from its unique three-dimensional structure.2 However, the HybA subunit itself could not even be isolated and purified as well as the whole complex (HybOCAB). We have recently succeeded in the expression and purification of HybA derived from the genome in Citrobacter sp. S77 as an E.coli recombinant protein. The recombinant HybA was successfully purified by several steps of column chromatography.The crystallization of the purified HybA has been tried under anaerobic conditions. At the same time, the characterization of HybA by measuring UV-VIS spectra was carried out to check the absorbance around 400 nm due to iron-sulfur clusters. The redox parameter of HybA was also measured by electrochemical method. The effect of HybA on the hydrogenase activity was measured by gas chromatography. In this poster, the characterization and crystallization of HybA will be presented.International Symposium on Diffraction Structural Biology 201