Metal Metalloproteins

IN SITU AND AFM OF SINGLE-METAL METALLOPROTEINS HORSE HEART CYTOCHROME C AND PSEUDOMONAS AERUGINOSA AZURIN... 

METALLOPROTEINS. Metalloproteins are either metal storage forms, as in the case of ferritin, or enzymes in which the metal atom participates in a catalyti-cally important manner. We encounter many examples throughout this book of the vital metabolic functions served by metalloenzymes. 

Metalloproteins contain metal atoms Ferritin Iron 35... 

Some of the critical enzymes in our cells are metalloproteins, large organic molecules made up of folded polymerized chains of amino acids that also include at least one metal atom. These metalloproteins are intensely studied by biochemists, because they control life and protect against disease. They have also been used to trace evolutionary paths. The d-block metals catalyze redox reactions, form components of membrane, muscle, skin, and bone, catalyze acid-base reactions, control the flow of energy and oxygen, and carry out nitrogen fixation. 

Cohen lA (1980) Metal-Metal Interactions in the Metalloporphyrins, Metalloproteins and Metalloenzymes. 40 1-37... 

TABLE 5 Ligand Preferences for Metals Commonly Found in Metalloproteins... 

The many redox reactions that take place within a cell make use of metalloproteins with a wide range of electron transfer potentials. To name just a few of their functions, these proteins play key roles in respiration, photosynthesis, and nitrogen fixation. Some of them simply shuttle electrons to or from enzymes that require electron transfer as part of their catalytic activity. In many other cases, a complex enzyme may incorporate its own electron transfer centers. There are three general categories of transition metal redox centers cytochromes, blue copper proteins, and iron-sulfur proteins. 

Cohen, I. A. Metal-Metal Interactions in Metalloporphyrins, Metalloproteins and Metallo-enzymes. Vol. 40, pp. 1-37. 

Injury to cells and tissues may enhance the toxicity of the active oxygen species by releasing intracellular transition metal ions (such as iron) into the surrounding tissue from storage sites, decompartmentalized haem proteins, or metalloproteins by interaction with delocalized proteases or oxidants. Such delocalized iron and haem proteins have the capacity to decompose peroxide to peroxyl and alkoxyl radicals, exacerbating the initial lesion. 

The fact that imidazole (Him) residues are particularly popular transition metal binding sites within metalloproteins is a major driving force for investigations of this heterocycle. The divalent... 

A number of zinc selenium complexes have now been characterized, with particular interest in the formation of zinc selenide semiconductors and quantum dots. In many cases analogous structures to those observed with thiol or thiolates are recorded. 77Se NMR is frequently used in characterization, and comparison with the sulfur equivalent is relevant. Zinc selenium compounds are of particular interest as precursors for metal/selenide materials and their relevance as models for selenocysteine-containing metalloproteins. 

Table 9 gives some cases where the rotational strengths of absorption bands have been measured in metalloproteins. At the present time these changes are not used to diagnose the nature of the ligands of the metal but rather they have been used to follow minor changes at the metal when substrates or inhibitors interact with the metals. The sensitivity of CD and MCD measurements to very small changes in the metal environment make them very attractive for protein/metal complex studies. 

Volume 226. Metallobiochemistry (Part C Spectroscopic and Physical Methods for Probing Metal Ion Environments in Metalloenzymes and Metalloproteins) Edited by James F. Riordan and Bert L. Vallee... 

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