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Characterization of the active site of a hydrogen sensor from Alcaligenes eutrophus
A J Pierik1, M Schmelz, O Lenz
1E.C. Slater Institute, Biochemistry, University of Amsterdam, The Netherlands.
Abstract:
A third hydrogenase was recently identified in the proteobacterium Alcaligenes eutrophus as a constituent of a novel H2-sensing multicomponent regulatory system. This regulatory hydrogenase (RH) has been overexpressed in cells deficient in both the NAD+-reducing [NiFe]-hydrogenase and the membrane-bound [NiFe]-hydrogenase. EPR, FTIR and activity studies of membrane-free extracts revealed that the RH has an active site much like that of standard [NiFe]-hydrogenases, i.e. a Ni-Fe site with two CN- groups and one CO molecule. Its catalytic power is low, but the RH is always active, insensitive to oxygen, and occurs in only two redox states.