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dc.contributor.authorSchut, Gerrit J.
dc.contributor.authorMohamed-Raseek, Nishya
dc.contributor.authorTokmina-Lukaszewska, Monika
dc.contributor.authorMulder, David W.
dc.contributor.authorNguyen, Diep M. N.
dc.contributor.authorLipscomb, Gina L.
dc.contributor.authorHoben, John P.
dc.contributor.authorPatterson, Angela
dc.contributor.authorLubner, Carolyn E.
dc.contributor.authorKing, Paul W.
dc.contributor.authorPeters, John W.
dc.contributor.authorBothner, Brian
dc.contributor.authorMiller, Anne-Frances
dc.contributor.authorAdams, Michael W. W.
dc.identifier.citationSchut, Gerrit J. , Nishya Mohamed-Raseek, Monika Tokmina-Lukaszewska, David W. Mulder, Diep M. N. Nguyen, Gina L. Lipscomb, John P. Hoben, Angela Patterson, Carolyn E. Lubner, Paul W. King, John W. Peters, Brian Bothner, Anne-Frances Miller, and Michael W. W. Adams. "The catalytic mechanism of electron bifurcating electron transfer flavoproteins (ETFs) involves an intermediary complex with NAD." Journal of Biological Chemistry (December 2018). DOI:10.1074/jbc.RA118.005653.en_US
dc.description.abstractElectron bifurcation plays a key role in anaerobic energy metabolism but it is a relatively new discovery and only limited mechanistic information is available on the diverse enzymes that employ it. Herein, we focused on the bifurcating electron transfer flavoprotein (ETF) from the hyperthermophilic archaeon Pyrobaculum aerophilum The EtfABCX enzyme complex couples NADH oxidation to the endergonic reduction of ferredoxin and exergonic reduction of menaquinone. We developed a model for the enzyme structure by using non-denaturing MS, cross-linking and homology modeling in which EtfA, B, and C each contained FAD, whereas EtfX contained two [4Fe-4S] clusters. On the basis of analyses using transient absorption, EPR and optical titrations with NADH or inorganic reductants with and without NAD+, we propose a catalytic cycle involving formation of an intermediary NAD+-bound complex. A charge transfer signal revealed an intriguing interplay of flavin semiquinones and a protein conformational change that gated electron transfer between the low- and high-potential pathways. We found that despite a common bifurcating flavin site, the proposed EtfABCX catalytic cycle is distinct from that of the genetically-unrelated bifurcating NADH-dependent ferredoxin NADP+ oxidoreductase (NfnI). The two enzymes particularly differed in the role of NAD+, the resting and bifurcating-ready states of the enzymes, how electron flow is gated, and in the two two-electron cycles constituting the overall four-electron reaction. We conclude that P. aerophilum EtfABCX provides a model catalytic mechanism that builds on and extends previous studies of related bifurcating ETF\'s and can be applied to the large bifurcating ETF family.en_US
dc.rightsThis Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).en_US
dc.titleThe catalytic mechanism of electron bifurcating electron transfer flavoproteins (ETFs) involves an intermediary complex with NADen_US
mus.citation.journaltitleJournal of Biological Chemistryen_US
mus.identifier.categoryChemical & Material Sciencesen_US
mus.relation.collegeCollege of Letters & Scienceen_US
mus.relation.departmentChemistry & Biochemistry.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.contributor.orcidBothner, Brian|0000-0003-1295-9609en_US
mus.contributor.orcidPeters, John W.|0000-0001-9117-9568en_US
mus.contributor.orcidTokmina-Lukaszewska, Monika|0000-0003-3298-8298en_US

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