Iron Cofactors: Nonhaem

Brian G Fox, University of Wisconsin, Madison, Wisconsin, USA

Published online: September 2005

DOI: 10.1038/npg.els.0003888

Proteins and enzymes with nonhaem iron centres display many functions: metal centres with primarily sulfur ligation are involved in electron transfer, electrophilic activation of hydroxyl groups, regulation of gene expression and fixation of N2; mononuclear and diiron centres with oxygen and nitrogen ligation have roles in various reactions with  O2 and in hydrolysis. The principles of their mechanisms of action are beginning to emerge from the considerable experimental data obtained on these proteins. Future research will attempt to extend this mechanistic understanding and to manipulate the enzymes to extend their already substantial catalytic capabilities.

Keywords: enzyme; iron; mechanism; structure

Figure 1. (a) Rubredoxin of Pyrococcus furiosus. (b) Heterocyst [2Fe–2S] of Anabaena. (c) [3Fe–4S] of inactive aconitase. (d) [4Fe–4S] of Escherichia coli endonuclease III.
Figure 2. Spatial orientation of MoFe and P clusters in dinitrogenase. Molybdenum is shown in green; calcium is shown in orange.
Figure 3. Mononuclear iron sites in catechol dioxygenases. (a) Intradiol Fe(iii) dioxygenase with 3,4-dihydroxybenzoate bound by catechol oxygens shown in purple. The displaced Tyr ligand is shown in orange. (b) ‘Two His–one carboxylate facial triad’ motif of extradiol Fe(ii) dioxygenases and other Fe(ii)-containing enzymes. Two water molecules (red) are also bound to iron.
Figure 4. Diiron centres in proteins. (a) Diferric state of ribonucleotide diphosphate reductase R2 component. The -oxo bridge is shown in green. (b) Diferric state of methane monooxygenase hydroxylase component. (c) Diferrous state of stearoyl-ACP 9 desaturase. (d) Oxyhaemerythrin. The -oxo bridge is shown in green; bound peroxide is shown in purple.
close
 Further Reading
    Beinert H, Holm RC and Münck E (1997) Iron–sulfur clusters: nature's modular, multipurpose structures. Science 277: 653–659.
    book Bertini I, Gray HB, Lippard SJ and Valentine JS (1994) Bioinorganic Chemistry. Mill Valley, CA: University Science Books.
    book Fox BG (1997) "Catalysis by non-heme iron-containing enzymes". In: Sinnott M (ed.) Comprehensive Biological Catalysis, vol. 3, pp. 261–348. London: Academic Press.
    book Fraústo da Silva JJR and Williams RJP (1993) The Biological Chemistry of the Elements. Oxford: Clarendon Press.
    Merkx M, Kopp DA, Sazinsky MH et al. (2001) Dioxygen activation and methane hydroxylation by soluble methane monooxygenase: a tale of two irons and three proteins. Angewandte Chemie-International Edition in English 40: 2782–2807.
    Que JrL and Ho RYN (1996) Dioxygen activation by enzymes with mononuclear non-heme iron active sites. Chemical Review 96: 2607–2624.
    Solomon EI (2000) Geometric and electronic structure/function correlations in non-heme iron enzymes. Chemical Review 100: 235–349.
    Wallar BJ and Lipscomb JD (1996) Dioxygen activation by enzymes containing binuclear non-heme iron clusters. Chemical Review 96: 2625–2657.

Related Sub-Topics:

Protein Structure | Proteins: Structure, Function, Metabolism | Enzymes: Structure and Action Mechanism
Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

Article Title: Iron Cofactors: Nonhaem
 
How to Cite close
Fox, Brian G(Sep 2005) Iron Cofactors: Nonhaem. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003888]