Metallothioneins are unusual, low-molecular-weight proteins of extremely high sulfur and metal content. They occur in varying abundance in parenchymatous tissues of vertebrates and invertebrates and have been identified also in some microorganisms. Unlike most other metalloproteins, the metallothioneins are, however, exceptional by their widely varying metal ion composition. This chapter presents an up-to-date account of the spectroscopic features of mammalian metallothioneins containing bivalent metals. The absorption spectra of metallothioneins are dominated by the transitions associated with metal binding. One of the most direct means by which bonding of the metal ions to thiolate groups in metallothionein was established is X-ray photoelectron spectroscopy. NMR spectra of metallothionein and of the apoprotein have been reported for materials from chicken liver, from equine, ovine, and human liver, and from equine kidney. C NMR spectrum has been reported for a preparation of rabbit-liver metal lothionein.
DNA and RNA polymerases are nucleotidyl transferases that catalyze the replication and transcription of the cellular genome. This chapter reviews the up-to-date knowledge about the intrinsic zinc ions in polymerases isolated from both prokaryotic and eukaryotic cells. It presents a short description of the role of zinc ions in the mechanism of DNA polymerases. The chapter emphases the recent developments of the metal studies of Escherichia coli RNA polymerase, as this is the enzyme in which the role of zinc ions has been most extensively studied. It discusses the biological implications of the roles of these intrinsic metal ions in gene replication and transcription. The structural role of metal ions may be more important in eukaryotic RNA polymerases, which contain a larger number of sub-units than do prokaryotic enzymes, where for example, wheat germ RNA polymerase II has 7 zinc ions per mol enzyme.
The increase in serum or plasma copper concentration found in all cancers studied has special significance since it has recently been recognized that many, if not all, tumor cells have decreased copper-dependent superoxide dismutase (SOD) enzymatic activity. Prior to 1969, occasional publications reported that sodium-3-(N-allylcuprothiouredo)-1-benzoate and cuprous iodide had anti-inflammatory activity and that Cu(II)(salicylate) had fever-lowering effects in various models of inflammation or fever. However, mixtures of copper salts and salicylic acid or ethyl salicylate in aqueous ethanol or glycerol-dimethysul-foxide solutions have recently been shown to have anti-inflammatory activity in a variety of animal models of inflammation following topical application. The lack of gastric irritation, the presence of antiulcer activity, and the enhanced anti-inflammatory activity of these complexes make this class of potentially useful antiarthritic drugs particularly promising since the arthritic syndrome is likely to include gastric ulcers.
