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

Leghemoglobin II. CHANGES IN CONFORMATION AND CHEMICAL REACTIVITY LINKED TO REACTION WITH A DISSOCIABLE LOW MOLECULAR WEIGHT LIGAND, X

Fish were maintained in sea water equilibrated with a gas mixture containing a non-equilibrium mixture of the three molecular species of oxygen, O18-O18 (mass 36), O18-O16 (mass 34), and O16-O16 (mass 32). Analyses in the mass spectrometer, of the gases secreted into the swim-bladder showed that no change in the relative abundance of these three molecular species had occurred during the secretory process and that therefore no exchange of atoms between oxygen molecules had occurred. Scission of the oxygen-oxygen bond probably does not occur during the transport process. It is concluded that the active transport of oxygen into the swim-bladder by the gas gland is a transport of molecular oxygen.

https://rupress.org/jgp/article-pdf/44/3/521/1242518/521.pdf

The Secretion of Oxygen into the Swim-bladder of Fish : I. The transport of molecular oxygen

On optima: the case of myoglobin-facilitated oxygen diffusion.

The cytoplasmic hemoglobin II from the gill of the clamLucina pectinata consists of 150 amino acid residues, has a calculatedMm of 17,476, including heme and an acetylated N-terminal residue. It retains the invariant residues Phe 44 at position CD1 and His 65 at the proximal position F8, as well as the highly conserved Trp 15 at position A12 and Pro 38 at position C2. The most likely candidate for the distal residue at position E7, based on the alignment with other globins, is Gln 65. However, optical and EPR spectroscopic studies of the ferri Hb II (Kraus, D. W., Wittenberg, J. B., Lu, J. F., and Peisach, J.,J. Biol. Chem.265, 16054–16059, 1990) have implicated a tyrosinate oxygen as the distal ligand. Modeling of theLucina Hb II sequence, using the crystal structure of sperm whale aquometmyoglobin, showed that Tyr 30 substituting for the Leu located at position B10 can place its oxygen within 2.8 A of the water molecule occupying the distal ligand position. This structural alteration is facilitated by the coordinate mutation of the residue at position CD4, from Phe 46 in the sperm whale myoglobin sequence to Leu 47 inLucina Hb II.

The amino acid sequence of hemoglobin II from the symbiont-harboring clam Lucina pectinata.

Studies on the Equilibria and Kinetics of the Reactions of Peroxidases with Ligands. III. The Dissociation of Carbon Monoxide from Carbon Monoxide Ferro-Horseradish Peroxidase*

Jonathan B. Wittenberg

Papers

Leghemoglobin II. CHANGES IN CONFORMATION AND CHEMICAL REACTIVITY LINKED TO REACTION WITH A DISSOCIABLE LOW MOLECULAR WEIGHT LIGAND, X

The Secretion of Oxygen into the Swim-bladder of Fish : I. The transport of molecular oxygen

On optima: the case of myoglobin-facilitated oxygen diffusion.

The amino acid sequence of hemoglobin II from the symbiont-harboring clam Lucina pectinata.

Studies on the Equilibria and Kinetics of the Reactions of Peroxidases with Ligands. III. The Dissociation of Carbon Monoxide from Carbon Monoxide Ferro-Horseradish Peroxidase*