Research supported by this grant in recent years has focused on what we have defined as the non-heme iron reductive paradigm for combating oxidative and nitrosative stress. This novel paradigm involves reductive scavenging of toxic reduced oxygen and nitrogen species by a group of bacterial and archaeal non-heme iron enzymes. Genetic evidence associates the functions of these enzymes in numerous bacterial and archaeal species. Based on genome sequences, these enzymes are found predominantly in air-sensitive bacteria, including those that constitute the majority of the normal human gut flora as well as human pathogens. These enzymes may protect against the oxidative and nitrosative burst of macrophages, which is the human host's initial response to infection. In the present renewal proposal, one specific aim focuses on the mechanism of reductive nitric oxide scavenging by a novel enzyme containing a combination of flavin and diiron cofactors at its active site. Single turnover experiments will be used to identify the Fe-NO species formed upon reactions of the diiron sites with nitric oxide and to determine their catalytic relevance. These themes are then logically extended to bacterial O2 sensing and signaling, induction of biofilm formation and virulence, all involving bacterial non-heme iron proteins. Enzymes from Vibrio cholerae, the bacterium causing epidemic cholerae, catalyzing formation and decay of the bacterial "second messenger", cyclic-di-guanosine monophosphate, are the focus in these latter two specific aims. These enzymes are widespread in bacteria but have not been found in higher eukaryotes. Inhibitors of these enzymes could, therefore, constitute new classes of antibiotics. Intelligent design of antibiotics requires an understanding of their catalytic and/or sensing/signaling mechanisms. These mechanisms are the overall goal of this research.
The enzymes proposed for study may provide protection to pathogenic bacteria against the oxidative and nitrosative burst of macrophages, which is the human host's initial response to infection. Sensing/signaling proteins from Vibrio cholerae, the bacterium causing epidemic cholera, are prominently featured in the proposed research. When the structure and function of these enzymes is understood, inhibitors of these enzymes could be designed as new classes of antibiotics.
|Miner, Kyle D; Kurtz Jr, Donald M (2016) Active Site Metal Occupancy and Cyclic Di-GMP Phosphodiesterase Activity of Thermotoga maritima HD-GYP. Biochemistry 55:970-9|
|Frederick, Rosanne E; Caranto, Jonathan D; Masitas, Cesar A et al. (2015) Dioxygen and nitric oxide scavenging by Treponema denticola flavodiiron protein: a mechanistic paradigm for catalysis. J Biol Inorg Chem 20:603-13|
|Caranto, Jonathan D; Weitz, Andrew; Giri, Nitai et al. (2014) A diferrous-dinitrosyl intermediate in the N2O-generating pathway of a deflavinated flavo-diiron protein. Biochemistry 53:5631-7|
|Okamoto, Yasunori; Onoda, Akira; Sugimoto, Hiroshi et al. (2014) H2O2-dependent substrate oxidation by an engineered diiron site in a bacterial hemerythrin. Chem Commun (Camb) 50:3421-3|
|Caranto, Jonathan D; Weitz, Andrew; Hendrich, Michael P et al. (2014) The nitric oxide reductase mechanism of a flavo-diiron protein: identification of active-site intermediates and products. J Am Chem Soc 136:7981-92|
|Miner, Kyle D; Klose, Karl E; Kurtz Jr, Donald M (2013) An HD-GYP cyclic di-guanosine monophosphate phosphodiesterase with a non-heme diiron-carboxylate active site. Biochemistry 52:5329-31|
|Okamoto, Yasunori; Onoda, Akira; Sugimoto, Hiroshi et al. (2013) Crystal structure, exogenous ligand binding, and redox properties of an engineered diiron active site in a bacterial hemerythrin. Inorg Chem 52:13014-20|
|Caranto, Jonathan D; Gebhardt, Linda L; MacGowan, Charles E et al. (2012) Treponema denticola superoxide reductase: in vivo role, in vitro reactivities, and a novel [Fe(Cys)(4)] site. Biochemistry 51:5601-10|
|Hayashi, Takahiro; Caranto, Jonathan D; Matsumura, Hirotoshi et al. (2012) Vibrational analysis of mononitrosyl complexes in hemerythrin and flavodiiron proteins: relevance to detoxifying NO reductase. J Am Chem Soc 134:6878-84|
|Fang, Han; Caranto, Jonathan D; Mendoza, Rosalinda et al. (2012) Histidine ligand variants of a flavo-diiron protein: effects on structure and activities. J Biol Inorg Chem 17:1231-9|
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