SIMILARITIES IN THE ARCHITECTURE OF THE ACTIVE-SITES OF NI-HYDROGENASES AND FE-HYDROGENASES DETECTED BY MEANS OF INFRARED-SPECTROSCOPY

Three groups that absorb in the 2100-1800-cm(-1) infrared spectral reg ion have recently been detected in Ni-hydrogenase from Chromatium vino sum [Bagley, K. A., Duin, E. C., Roseboom, W., Albracht, S. P. J. & Wo odruff, W. H. (1995) Biochemistry 34, 5527-5535]. To assess the signif icance and generality of this observation, we have carried out an infr ared-spectroscopic study of eight hydrogenases of three different type s (nickel, iron and metal-free) and of 11 other iron-sulfur and/or nic kel proteins. Infrared bands in the 2100-1800-cm(-1) spectral region w ere found in spectra of all Ni-hydrogenases and Fe-hydrogenases and we re absent from spectra of any of the other proteins, including a metal -free hydrogenase. The positions of these bands are dependent on the r edox state of the hydrogenase. The three groups in Ni-hydrogenases tha t are detected by infrared spectroscopy are assigned to the three unid entified small non-protein ligands that coordinate iron in the dinucle ar Ni/Fe active site as observed in the X-ray structure of the enzyme from Desulfovibrio gigas [Volbeda, A., Charon, M.-H., Piras, C., Hatch ikian, E. C., Frey, M. & Fontecilla-Camps, J. C. (1995) Nature 373, 58 0-587]. It is concluded that these groups occur exclusively in metal-c ontaining H-2-activating enzymes. It is proposed that the active sites of Ni-hydrogenases and of Fe-hydrogenases have a similar architecture , that is required for the activation of molecular hydrogen.