The Nitric Oxide Reductase Mechanism of Flavo-diiron Proteins

dc.contributor.advisorKurtz, Jr., Donald M.
dc.contributor.authorCaranto, Jonathan Douglas
dc.contributor.committeeMemberJarrett, Harry W.
dc.contributor.committeeMemberMusie, Ghezai T.
dc.contributor.committeeMemberTonzetich, Zachary J.
dc.descriptionThis item is available only to currently enrolled UTSA students, faculty or staff. To download, navigate to Log In in the top right-hand corner of this screen, then select Log in with my UTSA ID.
dc.description.abstractFlavo-diiron proteins (FDPs) contain both a non-heme diiron site and a flavin-mononucleotide binding domain. FDPs are widespread in O<sub>2</sub>-sensitive bacteria, archaea and also a few protozoan parasites. FDPs are implicated as oxidative or nitrosative stress protection enzymes. In some organisms, FDPs provide both protections. Biochemical evidence indicates that FDPs are the terminal components of a reductive dioxygen and/or nitric oxide scavenging pathway: O<sub>2</sub> + 4 e<super>-</super> + 4 H<super>+</super> &rarr; 2 H<sub>2</sub>O 2 NO + 2 e<super>-</super> + 2 H<super>+</super> &rarr; N<sub>2</sub>O + H<sub>2</sub>O The following research focused on characterizing the FDP NOR mechanism. Steady-state activity assays provide little information about NOR pathway intermediates and thus, rapid-mixing techniques were used to obtain pre-steady state kinetics and spectroscopic features of intermediates along the NOR pathway. The NOR pathway was determined to proceed via an antiferromagnetically coupled diferrous-dinitrosyl intermediate and does not require FMNH<sub>2</sub> to catalyze N-N bond formation. The implication of this work on diiron site reactivity towards NO reduction is discussed. In addition to the wild-type enzyme, FDP from Thermotoga maritima was mutated so as to replace an iron-coordinating histidine with either a weaker donor (asparagine) or a non-coordinating residue (alanine). Surprisingly, the steady-state and pre-steady-state O<sub>2</sub>R and NOR activities did not exhibit significant changes compared to the wild-type protein.
dc.format.extent219 pages
dc.subjectFlavo-diiron protein
dc.subjectnitric oxide
dc.subjectnon-heme iron
dc.subject.classificationInorganic chemistry
dc.titleThe Nitric Oxide Reductase Mechanism of Flavo-diiron Proteins
dcterms.accessRightspq_closed of Texas at San Antonio of Philosophy


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