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The coordination sphere of iron-sulfur clusters: lessons from site-directed mutagenesis experiments

  • J.-M. Moulis
  • Valérie Davasse
  • Marie-Pierre Golinelli
  • Jacques Meyer
  • Isabelle Quinkal
MINIREVIEW

Abstract

 Cysteine is the ubiquitous ligand of iron-sulfur clusters in proteins, although chemical models have indicated that functional groups other than thiolates can coordinate iron in iron-sulfur compounds. Only a small number of naturally occurring examples of hydroxyl, histidinyl or carboxyl coordination have been clearly established but many others are suspected. Quite a few site-directed mutagenesis experiments have been aimed at replacing the cysteine ligands of iron-sulfur centers by other amino acids in various systems. The available data set shows that substituting one ligand, even by another functional residue, is very often destabilizing enough to impair cluster assembly; in some cases, the apoprotein cannot even be detected. One for one replacements have been demonstrated, but they have been so far almost exclusively confined to clusters with no more than one or two iron atoms. In contrast, changes of the cluster nuclearity or recruitment of free cysteine residues seem preferred ways for proteins containing larger clusters to cope with removal of a ligand, rather than using coordinating amino acids bearing different chemical functions. Furthermore, the possibility of replacing cysteines by other residues as ligands in iron-sulfur proteins does not uniquely depend on the ability of the cluster to accept other kinds of coordination than cysteinate; other factors such as the local flexibility of the polypeptide chain, the accessibility of the solvent and the electronic distribution on the active centers may also play a prominent role.

Key words Site-directed mutagenesis Iron-sulfur Ligand exchange Cluster conversion 

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Copyright information

© Society of Biological Inorganic Chemistry 1996

Authors and Affiliations

  • J.-M. Moulis
    • 1
  • Valérie Davasse
    • 1
  • Marie-Pierre Golinelli
    • 1
  • Jacques Meyer
    • 1
  • Isabelle Quinkal
    • 1
  1. 1.CEA, Département de Biologie Moléculaire et Structurale, Laboratoire des Métalloprotéines, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France Tel.: +33 76885623; fax +33 76889808; e-mail: moulis@ebron.ceng.cea.frFR

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