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. 1975 Jan;72(1):231–234. doi: 10.1073/pnas.72.1.231

The Acid-Base Properties, Hydrolytic Mechanism, and Susceptibility to O2 Oxidation of Fe4S4(SR)4-2 Clusters

Thomas C Bruice 1, Richard Maskiewicz 1,*, Robert Job 1
PMCID: PMC432277  PMID: 16592211

Abstract

The iron-sulfur cluster compounds Fe4S4(SR)4-2 [where —SR = —SCH3, —S—C(CH3)3, and —S— CH2—CH(CH3)2] have been found to represent the base species of weak acids of pKa comparable to that of carboxylic acids. The acid species Fe4S4(SR)4H- is most subject to reaction with O2 and to acid-catalyzed solvolysis, while the base species Fe4S4(SR)4-2 most readily undergoes ligand exchange. The kinetics for hydrolysis of the isobutyl mercaptide cluster salt has been investigated in detail and a mechanism involving the stepwise process [Formula: see text] has been proposed. The importance of the acid-base equilibria in determining the reactivity of the iron-sulfur clusters and its possible importance as a factor in the determination of the potentials of ferredoxins and high potential iron protein are discussed.

Keywords: ferredoxins, high potential iron protein, iron-sulfur cluster compounds, acid labile sulfur, hydrolysis

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Averill B. A., Herskovitz T., Holm R. H., Ibers J. A. Synthetic analogs of the active sites of iron-sulfur proteins. II. Synthesis and structure of the tetra(mercapto-m 3 -sulfido-iron) clusters, (Fe 4 S 4 (SR) 4 ) 2- . J Am Chem Soc. 1973 May 30;95(11):3523–3534. doi: 10.1021/ja00792a013. [DOI] [PubMed] [Google Scholar]
  2. Cammack R. "Super-reduction" of chromatium high-potential iron-sulphur protein in the presence of dimethyl sulphoxide. Biochem Biophys Res Commun. 1973 Sep 18;54(2):548–554. doi: 10.1016/0006-291x(73)91457-5. [DOI] [PubMed] [Google Scholar]
  3. Carter C. W., Jr, Kraut J., Freer S. T., Alden R. A., Sieker L. C., Adman E., Jensen L. H. A comparison of Fe 4 S 4 clusters in high-potential iron protein and in ferredoxin. Proc Natl Acad Sci U S A. 1972 Dec;69(12):3526–3529. doi: 10.1073/pnas.69.12.3526. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. DePamphilis B. V., Averill B. A., Herskovitz T., Que L., Jr, Holm R. H. Synthetic analogs of the active sites of iron-sulfur proteins. VI. Spectral and redox characteristics of the tetranuclear clusters (Fe4S4(SR)4).2-. J Am Chem Soc. 1974 Jun 26;96(13):4159–4167. doi: 10.1021/ja00820a017. [DOI] [PubMed] [Google Scholar]
  5. Herskovitz T., Averill B. A., Holm R. H., Ibers J. A., Phillips W. D., Weiher J. F. Structure and properties of a synthetic analogue of bacterial iron--sulfur proteins. Proc Natl Acad Sci U S A. 1972 Sep;69(9):2437–2441. doi: 10.1073/pnas.69.9.2437. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Holm R. H., Averill B. A., Herskovitz T., Frankel R. B., Gray H. B., Siiman O., Grunthaner F. J. Equivalence of metal centers in the iron-sulfur protein active site analogs (Fe4S4(SR)4)2-. J Am Chem Soc. 1974 Apr 17;96(8):2644–2646. doi: 10.1021/ja00815a071. [DOI] [PubMed] [Google Scholar]
  7. Holm R. H., Phillips W. D., Averill B. A., Mayerle J. J., Herskovitz T. Synthetic analogs of the active sites of iron-sulfur proteins. V. Proton resonance properties of the tetranuclear clusters (Fe4S4(SR)4). Evidence for dominant contact interactions. J Am Chem Soc. 1974 Apr 3;96(7):2109–2117. doi: 10.1021/ja00814a020. [DOI] [PubMed] [Google Scholar]
  8. Kennedy S. C., Rauner R., Gawron O. On pig heart aconitase. Biochem Biophys Res Commun. 1972 May 26;47(4):740–745. doi: 10.1016/0006-291x(72)90554-2. [DOI] [PubMed] [Google Scholar]
  9. Orme-Johnson W. H. Iron-sulfur proteins: structure and function. Annu Rev Biochem. 1973;42(0):159–204. doi: 10.1146/annurev.bi.42.070173.001111. [DOI] [PubMed] [Google Scholar]
  10. Que L., Jr, Bobrik M. A., Ibers J. A., Holm R. H. Synthetic analogs of the active sites of iron-sulfur proteins. VII. Ligand substitution reactions of the tetranuclear clusters (Fe4S4(SR)4)2- and the structure of ((CH3)4N)2(Fe4S4(SC6H5)4). J Am Chem Soc. 1974 Jun 26;96(13):4168–4178. doi: 10.1021/ja00820a018. [DOI] [PubMed] [Google Scholar]
  11. Que L., Jr, Bobrik M. A., Ibers J. A., Holm R. H. Synthetic analogs of the active sites of iron-sulfur proteins. VII. Ligand substitution reactions of the tetranuclear clusters (Fe4S4(SR)4)2- and the structure of ((CH3)4N)2(Fe4S4(SC6H5)4). J Am Chem Soc. 1974 Jun 26;96(13):4168–4178. doi: 10.1021/ja00820a018. [DOI] [PubMed] [Google Scholar]
  12. Sweeney W. V., Bearden A. J., Rabinowitz J. C. The electron paramagnetic resonance of oxidized clostridial ferredoxins. Biochem Biophys Res Commun. 1974 Jul 10;59(1):188–194. doi: 10.1016/s0006-291x(74)80192-0. [DOI] [PubMed] [Google Scholar]

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