| STRUCTURE |
Author using X-ray structure analysis, mass spectrometry, and other techniques to determine the structure of the active sites of [NiFe]-hydrogenases and to find out which atoms are responsible for activating molecular hydrogen. "Although many crystal structures of the [NiFe] active site are now available, there is still uncertainty about the structure," he tells C&EN. "For example, the iron atom has four nonprotein ligands in the oxidized form. Three of these are diatomic ligands, and one is monatomic or its hydride." Two years ago, author and coworkers presented mass spectroscopic evidence that SO, a ligand that had never previously been reported in biomolecules, is present in the active site of a [NiFe]-hydrogenase obtained from a bacterium known as Desulfovibrio vulgaris Miyazaki. The group also reported that bands in the Fourier transform infrared spectrum of the hydrogenase are ascribable to CO and CN ligands. "We showed that SO, CO, or CN could be candidates for diatomic ligands and S or SH for the monatomic ligands. "Other groups claim that the diatomic ligands should be CO or CN and the monatomic ligand may be O or OH. However, we showed that when our [NiFe]-hydrogenase is activated--that is, reduced by hydrogen--it always liberates hydrogen sulfide." Armstrong PHOTO BY MICHAEL FREEMANTLE HYDROGEN ACTIVATION in most [NiFe]-hydrogenases is reversibly inhibited by oxygen and carbon monoxide. Author`s group solved 10 crystal structures to determine the exact site to which the competitive inhibitor carbon monoxide reversibly coordinates in a CO-bound [NiFe]-hydrogenase. The research group showed that carbon monoxide is coordinated to the Ni atom and not the Fe atom. |
| UPDATE | 07.02 |
| AUTHOR | This data is not available for free |
| LITERATURE REF. | This data is not available for free |
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