Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1797, Issue 2, Pages 304-313Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2009.11.002
Keywords
[NiFe] hydrogenase; Desulfovibrio vulgaris; Carbon monoxide inhibition; Spectro-electrochemistry; Rapid-scan FTIR; EPR
Categories
Funding
- Max Planck Society
- EU/Energy Network [212508, Bio H2, 03SF0355C]
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X-ray crystallographic studies [Ogata et al., J. Am. Chem. Soc. 124 (2002) 11628-11635] have shown that carbon monoxide binds to the nickel ion at the active site of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F and inhibits its catalytic function. In the present work spectroscopic aspects of the CO inhibition for this bacterial organism are reported for the first time and enable a direct comparison with the existing crystallographic data. The binding affinity of each specific redox state for CO is probed by FTIR spectro-electrochemistry. It is shown that only the physiological state Ni-Sl(a) reacts with CO. The CO-inhibited product state is EPR-silent (Ni2+) and exists in two forms, Ni-SCO and Ni-SCOred. At very negative potentials, the exogenous CO is electrochemically detached from the active site and the active Ni-R states are obtained. At temperatures below 100 K, photodissociation of the extrinsic CO from the Ni-SCO state results in Ni-Sl(a) that is identified to be the only light-induced state. In the dark rebinding of CO takes place; the recombination rate constants are of biexponential character and the activation barrier is determined to be approximately 9 kJ mol(-1). In addition, formation of a paramagnetic CO-inhibited state (Ni-CO) was observed that results from the interaction of carbon monoxide with the Ni-L state. It is proposed that the nickel in Ni-CO is in a formal monovalent state (Ni1+). (C) 2009 Elsevier B.V. All rights reserved.
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