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The hydrogenase maturation protein HypE serves an essential function in the biosynthesis of the nitrile group, which is subsequently coordinated to Fe as CN(-) ligands in [Ni-Fe] hydrogenase. Here, we present the crystal structures of HypE from Desulfovibrio vulgaris Hildenborough in the presence and in the absence of ATP at a resolution of 2.0 A and 2.6 A, respectively. Comparison of the apo structure with the ATP-bound structure reveals that binding ATP causes an induced-fit movement of the N-terminal portion, but does not entail an overall structural change. The residue Cys341 at the C terminus, whose thiol group is supposed to be carbamoylated before the nitrile group synthesis, is completely buried within the protein and is located in the vicinity of the gamma-phosphate group of the bound ATP. This suggests that the catalytic reaction occurs in this configuration but that a conformational change is required for the carbamoylation of Cys341. A glutamate residue is found close to the thiol group as well, which is suggestive of deprotonation of the carbamoyl group at the beginning of the reactions.

Crystal structures of hydrogenase maturation protein HypE in the Apo and ATP-bound forms., Shomura Y, Komori H, Miyabe N, Tomiyama M, Shibata N, Higuchi Y, J Mol Biol. 2007 Sep 28;372(4):1045-54. Epub 2007 Jul 26. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17706667 17706667]

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