1. Stepwise [FeFe]-hydrogenase H-cluster assembly revealed in the structure of [HydA.sup.ΔEFG]
- Author
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Mulder, David W., Boyd, Eric S., Sarma, Ranjana, Lange, Rachel K., Endrizzi, James A., Broderick, Joan B., and Peters, John W.
- Subjects
Genes -- Research ,Enzymes -- Physiological aspects -- Research -- Genetic aspects ,Hydrogenation -- Research ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
Complex enzymes containing Fe-S clusters are ubiquitous in nature, where they are involved in a number of fundamental processes including carbon dioxide fixation, nitrogen fixation and hydrogen metabolism (1,2). Hydrogen metabolism is facilitated by the activity of three evolutionarily and structurally unrelated enzymes: the [NiFe]-hydrogenases, [FeFe]-hydrogenases and [Fe]-hydrogenases (3,4) (Hmd). The catalytic core of the [FeFe]-hydrogenase (HydA), termed the H-cluster, exists as a [4Fe-4S] subcluster linked by a cysteine thiolate to a modified 2Fe subcluster with unique non-protein ligands (5,6). The 2Fe subcluster and non-protein ligands are synthesized by the hydrogenase maturation enzymes HydE, HydF and HydG; however, the mechanism, synthesis and means of insertion of H-cluster components remain unclear (7-10). Hereweshowthe structure of [HydA.sup.ΔDEFG] (HydA expressed in a genetic background devoid of the active site H-cluster biosynthetic genes hydE, hydF and hydG) revealing the presence of a [4Fe-4S] cluster and an open pocket for the 2Fe subcluster. The structure indicates that H-cluster synthesis occurs in a stepwise manner, first with synthesis and insertion of the [4Fe-4S] subcluster by generalized host-cell machinery (11,12) and then with synthesis and insertion of the 2Fe subcluster by specialized hydE-, hydF- and hydG-encoded maturation machinery (7-10). Insertion of the 2Fe subcluster presumably occurs through a cationically charged channel that collapses following incorporation, as a result of conformational changes in two conserved loop regions. The structure, together with phylogenetic analysis, indicates that HydA emerged within bacteria most likely from a Narl-like ancestor lacking the 2Fe subcluster, and that this was followed by acquisition in several unicellular eukaryotes., The biosynthesis and assembly of active-site metallo-cofactors requires multiple enzymes, scaffolds and carriers (2,11,13). For [FeFe]-hydrogenases, the gene products HydE, HydF and HydG are required for the maturation of the [...]
- Published
- 2010
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