The canonical structural motif for co-ordination of non-haem ferrous iron in metal-dependent oxygenases is a facial triad of two histidine residues and one aspartate or glutamate residue. This so-called 2-His-1-carboxylate metallocentre is often accommodated in a double-stranded β-helix fold with the iron-co-ordinating residues located in the rigid core structure of the protein. At the sequence level, the metal ligands are arranged in a HXD/E…H motif (where the distance between the conserved histidine residues is variable). Interestingly, cysteine dioxygenase, among a growing number of other iron(II) oxygenases, has the carboxylate residue replaced by another histidine. In the present review, we compare the properties of 3-His and 2-His-1-carboxylate sites based on current evidence from high-resolution crystal structures, spectroscopic characterization of the metal centres and results from mutagenesis studies. Although the overall conformation of the two metal sites is quite similar, the carboxylate residue seems to accommodate a slightly closer co-ordination distance than the counterpart histidine. The ability of the 2-His-1-carboxylate site to fit a site-directed substitution by an alternatively co-ordinating or non-co-ordinating residue with retention of metal-binding capacity and catalytic function varies among different enzymes. However, replacement by histidine disrupted the activity in the three iron(II) oxygenases examined so far.
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Conference Article|
November 19 2008
Structural and functional comparison of 2-His- 1-carboxylate and 3-His metallocentres in non-haem iron(II)-dependent enzymes
Stefan Leitgeb;
Stefan Leitgeb
1Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12/I, A-8010 Graz, Austria
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Bernd Nidetzky
Bernd Nidetzky
1
1Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12/I, A-8010 Graz, Austria
1To whom correspondence should be addressed (email bernd.nidetzky@tugraz.at).
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Publisher: Portland Press Ltd
Received:
July 23 2008
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem Soc Trans (2008) 36 (6): 1180–1186.
Article history
Received:
July 23 2008
Citation
Stefan Leitgeb, Bernd Nidetzky; Structural and functional comparison of 2-His- 1-carboxylate and 3-His metallocentres in non-haem iron(II)-dependent enzymes. Biochem Soc Trans 1 December 2008; 36 (6): 1180–1186. doi: https://doi.org/10.1042/BST0361180
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