Metal ions may play an essential role in chromatin organization and, thus, be main actors in the gene expression drama. A model is proposed here for the interaction of DNA‐binding transcriptional regulatory proteins with histone H3 via coordinated metal ions and discussed in relation to the conversion of nucleosomal ‘closed’ to ‘open’ states.

Protein redox reactions are one of the most basic and important biochemical actions. As amino acids are weak redox mediators, most protein redox functions are undertaken by protein cofactors, which include organic ligands and transition metal ions. Since both kinds of redox cofactors were available in the pre‐protein RNA world, it is challenging to explore which one was more involved in redox processes of primitive proteins? In this paper, using an examination of the redox cofactor usage of putative ancient (...) proteins, we infer that organic ligands participated more frequently than transition metals in redox reactions of primitive proteins, at least as protein cofactors. This is further supported by the relative abundance of amino acids in the primordial world. Supplementary material for this article can be found on the BioEssays website. BioEssays 30:766–771, 2008. © 2008 Wiley Periodicals, Inc. (shrink)