On the active sites of the [NiFe] hydrogenase from Desulfovibrio gigas. Mossbauer and redox-titration studies

On the active sites of the [NiFe] hydrogenase from Desulfovibrio gigas. Mossbauer and redox-titration studies, Huynh, B. H., Patil D. S., Moura I., Teixeira M., Moura J. J., Dervartanian D. V., Czechowski M. H., Prickril B. C., Peck, H. D. Jr., and Legall J. , J Biol Chem, Jan 15, Volume 262, Number 2, p.795-800, (1987)


The [NiFe] hydrogenase isolated from Desulfovibrio gigas was poised at different redox potentials and studied by Mossbauer spectroscopy. The data firmly establish that this hydrogenase contains four prosthetic groups: one nickel center, one [3Fe-xS], and two [4Fe-4S] clusters. In the native enzyme, both the nickel and the [3Fe-xS] cluster are EPR-active. At low temperature (4.2 K), the [3Fe-xS] cluster exhibits a paramagnetic Mossbauer spectrum typical for oxidized [3Fe-xS] clusters. At higher temperatures (greater than 20 K), the paramagnetic spectrum collapses into a quadrupole doublet with parameters magnitude of delta EQ magnitude of = 0.7 +/- 0.06 mm/s and delta = 0.36 +/- 0.06 mm/s, typical of high-spin Fe(III). The observed isomer shift is slightly larger than those observed for the three-iron clusters in D. gigas ferredoxin II (Huynh, B. H., Moura, J. J. G., Moura, I., Kent, T. A., LeGall, J., Xavier, A. V., and Munck, E. (1980) J. Biol. Chem. 255, 3242-3244) and in Azotobacter vinelandii ferredoxin I (Emptage, M. H., Kent, T. A., Huynh, B. H., Rawlings, J., Orme-Johnson, W. H., and Munck, E. (1980) J. Biol. Chem. 255, 1793-1796) and may indicate a different iron coordination environment. When D. gigas hydrogenase is poised at potentials lower than -80 mV (versus normal hydrogen electrode), the [3Fe-xS] cluster is reduced and becomes EPR-silent. The Mossbauer data indicate that the reduced [3Fe-xS] cluster remains intact, i.e. it does not interconvert into a [4Fe-4S] cluster. Also, the electronic properties of the reduced [3Fe-xS] cluster suggest that it is magnetically isolated from the other paramagnetic centers.


0021-9258 (Print)0021-9258 (Linking)Journal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

Related External Link