Publication Date:
2010-04-27
Description:
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. Hydrogen metabolism is facilitated by the activity of three evolutionarily and structurally unrelated enzymes: the [NiFe]-hydrogenases, [FeFe]-hydrogenases and [Fe]-hydrogenases (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. 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. Here we show the structure of HydA(DeltaEFG) (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 and then with synthesis and insertion of the 2Fe subcluster by specialized hydE-, hydF- and hydG-encoded maturation machinery. 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 Nar1-like ancestor lacking the 2Fe subcluster, and that this was followed by acquisition in several unicellular eukaryotes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mulder, David W -- Boyd, Eric S -- Sarma, Ranjana -- Lange, Rachel K -- Endrizzi, James A -- Broderick, Joan B -- Peters, John W -- England -- Nature. 2010 May 13;465(7295):248-51. doi: 10.1038/nature08993. Epub 2010 Apr 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20418861" target="_blank"〉PubMed〈/a〉
Keywords:
Catalytic Domain
;
Chlamydomonas reinhardtii/*enzymology
;
Clostridium/enzymology
;
Crystallography, X-Ray
;
Hydrogen/metabolism
;
Hydrogenase/*chemistry/genetics/*metabolism
;
Iron/*metabolism
;
Models, Molecular
;
Nitrogenase/metabolism
;
Phylogeny
;
Protein Conformation
;
Sulfur/metabolism
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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