Iron-sulfur cluster properties

Noodleman L, Pique ME et al (2007) Iron-sulfur clusters properties and functions. In Wiley encyclopedia of chemical biology. Wiley, New York... 

PS Brereton, FJM Verhagen, ZH Zhou, MWW Adams. Effect of iron-sulfur cluster environment m modulating the thermodynamic properties and biological function of ferredoxm from Pyrococcus furiosus. Biochemistry 37 7351-7362, 1998. 

For the cytochrome c-plastocyanin complex, the kinetic effects of cross-linking are much more drastic while the rate of the intracomplex transfer is equal to 1000 s in the noncovalent complex where the iron-to-copper distance is expected to be about 18 A, it is estimated to be lower than 0.2 s in the corresponding covalent complex [155]. This result is all the more remarkable in that the spectroscopic and thermodynamic properties of the two redox centers appear weakly affected by the cross-linking process, and suggests that an essential segment of the electron transfer path has been lost in the covalent complex. Another system in which such conformational effects could be studied is the physiological complex between tetraheme cytochrome and ferredoxin I from Desulfovibrio desulfuricans Norway the spectral and redox properties of the hemes and of the iron-sulfur cluster are found essentially identical in the covalent and noncovalent complexes and an intracomplex transfer, whose rate has not yet been measured, takes place in the covalent species [156]. 

Some characteristic properties of iron-sulfur clusters in proteins result from interactions with invariant amino acid fragments around the clusters. In particular, clusters in peptide environments exhibit positive shifts in redox potentials relative to those in nonpeptide environments. Such shifts are observed for a variety of oligopeptide model complexes of IFe, 2Fe-2S, and 4Fe-4S proteins. 

A recent review on abiological iron-sulfur clusters should be the primary entry reference to anyone wishing to gain information on this wide field [2]. Indeed, Ogino et al. provide a comprehensive source of data, of synthetic, structural, spectroscopic, and electrochemical nature, on many synthetic iron-sulfur clusters. The electrochemical properties of Roussin s black anion [3] have been investigated... 

An excellent, still up-to-date survey on chemical properties, structures and biological functions of iron-sulfur clusters has been given by Beinert.174 As a more general survey of EPR properties of iron-sulfur proteins we recommend a reference which was also quoted in our earlier report.175... 

Fig. 10. Hypothetical reaction cycle for D. gigas hydrogenase, based on the EPR and redox properties of the nickel (Table II). Only the nickel center and one [4Fe-4S] cluster are shown. Step 1 enzyme, in the activated conformation and Ni(II) oxidation state, causes heterolytic cleavage of H2 to produce a Ni(II) hydride and a proton which might be associated with a ligand to the nickel or another base in the vicinity of the metal site. Step 2 intramolecular electron transfer to the iron-sulfur cluster produces a protonated Ni(I) site (giving the Ni-C signal). An alternative formulation of this species would be Ni(III) - H2. Step 3 reoxidation of the iron-sulfur cluster and release of a proton. Step 4 reoxidation of Ni and release of the other proton.

Aconitase was the first protein to be identified as containing a catalytic iron-sulfur cluster [24-26]. It was also readily established that the redox properties of the [4Fe-4S](2+ 1+) cluster do not play a role of significance in biological functioning the 1 + oxidation state has some 30% of the activity of the 2+ state [25], Since then several other enzymes have been identified or proposed to be nonredox iron-sulfur catalysts. They are listed in Table 2. It appears that all are involved in stereospecific hydration reactions. However, these proteins are considerably less well characterized than aconitase. In particular, no crystal structural information is available yet. Therefore, later we summarize structural and mechanistic information on aconitase, noting that many of the basic principles are expected to be relevant to the other enzymes of Table 2. 

A catalytic redox iron-sulfur cluster is defined by having two properties (1) the coordination of the cluster (or one of its constituting atoms) changes during catal-... 

Carney, M.J., J.A. Kovacs, Y.-P. Zhang, G.C. Papaefthymiou, K. Spartalian, R.B. Frankel, and R.H. Holm. 1987. Comparative electronic properties of vanadium-iron-sulfur and molybdenum-iron-sulfur clusters containing isoelectronic cubane-type [VFe3S4]2+ and [MoFe3S4]3+ cores. Inorg. Chem. 26 719-724. 

Other biomimetic reactions are based on the catalytic properties of metal ions. Many enzymes require metal ions that function, in one way or another, in oxidation-reduction processes. The wide range of such metal-ion reactions precludes mentioning more than a few in addition to the iron-porphyrin class, and in addition to chlorophyll, a number of enzymes require cobalamin as cofactor ferridoxin and high-potential iron proteins require iron-sulfur clusters, and nitrog-... 

You JF, Snyder BS, Papaefthymiou GC, Holm RH. On the molecular/solid state boundary. A cyclic iron-sulfur cluster of nuclearity of eighteen synthesis, structure and properties. 

---