For present purposes, a protein-bound metal site consists of one or more metal ions and all protein side chain and exogenous bridging and terminal ligands that define the first coordination sphere of each metal ion. Such sites can be classified into five basic types with the indicated functions: (1) structural -- configuration (in part) of protein tertiary and/or quaternary structure; (2) storage -- uptake, binding, and release of metals in soluble form: (3) electron transfer -- uptake, release, and storage of electrons; (4) dioxygen binding -- metal-O{sub 2} coordination and decoordination; and (5) catalytic -- substrate binding, activation, and turnover. The authors present here a classification and structure/function analysis of native metal sites based on these functions, where 5 is an extensive class subdivided by the type of reaction catalyzed. Within this purview, coverage of the various site types is extensive, but not exhaustive. The purpose of this exposition is to present examples of all types of sites and to relate, insofar as is currently feasible, the structure and function of selected types. The authors largely confine their considerations to the sites themselves, with due recognition that these site features are coupled to protein structure at all levels. In themore » next section, the coordination chemistry of metalloprotein sites and the unique properties of a protein as a ligand are briefly summarized. Structure/function relationships are systematically explored and tabulations of structurally defined sites presented. Finally, future directions in bioinorganic research in the context of metal site chemistry are considered. 620 refs.« less

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Structural and Functional Aspects of Metal Sites in Biology

Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.

/pdf/myeloperoxidase-friend-and-foe-ymb1dqwgv0.pdf

Myeloperoxidase: friend and foe

Mechanisms and applications of plant growth promoting rhizobacteria: Current perspective

ion from the Sugar Moiety Wendy Knapp Pogozelski† and Thomas D. Tullius*,‡ Department of Chemistry, State University of New York at Geneseo, Geneseo, New York 14454, and Department of Chemistry, Boston University, Boston, Massachusetts 02215 Received August 27, 1997 (Revised Manuscript Received February 26, 1998)

Oxidative Strand Scission of Nucleic Acids: Routes Initiated by Hydrogen Abstraction from the Sugar Moiety.

On the function and mechanism of action of peroxidases

Toadfish (Opsanus tau) were maintained at 50 m depth, 6 atm total pressure. The partial pressures of argon and nitrogen in the gases brought into the experi mentally emptied swimbladder exceed the ambient pressures. The fraction of ni trogen in the gases brought into the swimbladder is nearly independent of depth. This finding is inconsistent with an earlier hypothesis that active oxygen secretion, by forming minute bubbles, drives nitrogen secretion. Toadfish were maintained in seawater equilibrated with mixtures containing oxygen, nitrogen, helium (in previous experiments), neon, argon, krypton and xenon. The more soluble gases are enriched in the mixture brought into the swimbladder, so that the composition of the inert gases brought into the swimbladder is similar to the composition of the gases dissolved in blood plasma. The enhancements, ([Gas/N2J,,@1@A·[Gas/ N2]ambicnt), of the gases in the mixture brought into the swimbladder are proportional to the solubility of the gases in water. These facts support the hypothesis that salting out of inert gases elevates the partial pressure of nitrogen and other inert gases in the gas gland blood vessels. High gas pressures may be generated by counter-current multiplication of this initial effect.

Secretion of nitrogen into the swimbladder of fish. ii. molecular mechanism. secretion of noble gases

Reactivity and function of leghemoglobin1

Crystallization and preliminary data for the ferric form of Lucina pectinata hemoglobin I.

the common carp lives in stagnant ponds where it must weather long periods of low environmental oxygen pressure. In a dramatic adaptation to life in this environment, carp and a few related fishes develop a novel myoglobin-like protein, myoglobin-2, found only in the brain ([3][1]), where it may

https://www.physiology.org/doi/pdf/10.1152/ajpregu.00677.2011

Editorial focus: Myoglobin-2, an adaptation for life at low oxygen pressure. Focus on: "Functional differentiation of myoglobin isoforms in the hypoxia-tolerant carp".

The Puerto Rican clam Lucina pectinata, a bivalve mollusc, has three cytoplasmic Hbs associated with its gill: HbI, HbII and HbIII. The clam utilizes these three Hbs in symbiosis with intracellular chemoautotrophic bacteria (1). These bacteria reside in the gill of the clam where its requirement for O2 and hydrogen sulfide is provided by the clam via the Hbs (2)

Jonathan B. Wittenberg

Papers

Secretion of nitrogen into the swimbladder of fish. ii. molecular mechanism. secretion of noble gases

Reactivity and function of leghemoglobin1

Crystallization and preliminary data for the ferric form of Lucina pectinata hemoglobin I.

Editorial focus: Myoglobin-2, an adaptation for life at low oxygen pressure. Focus on: "Functional differentiation of myoglobin isoforms in the hypoxia-tolerant carp".

Partial Amino Acid Sequence of Hemoglobin II from Lucina pectinata