Show simple item record

dc.contributor.authorDuan, H. D.
dc.contributor.authorLubner, Carolyn E.
dc.contributor.authorTokmina-Lukaszewska, Monika
dc.contributor.authorGauss, George H.
dc.contributor.authorBothner, Brian
dc.contributor.authorKing, Paul W.
dc.contributor.authorPeters, John W.
dc.contributor.authorMiller, A. F.
dc.identifier.citationDuan, HD, CE Lubner, Monika Tokmina-Lukaszewska, George H. Gauss, Brian Bothner, PW King, Peters JW, and AF Miller. "Distinct properties underlie flavin-based electron bifurcation in a novel electron transfer flavoprotein FixAB from Rhodopseudomonas palustris." Journal of Biological Chemistry 293 (February 2018). DOI: 10.1074/jbc.RA117.000707.en_US
dc.description.abstractA newly recognized third fundamental mechanism of energy conservation in biology, electron bifurcation, uses free energy from exergonic redox reactions to drive endergonic redox reactions. Flavin-based electron bifurcation furnishes low-potential electrons to demanding chemical reactions, such as reduction of dinitrogen to ammonia. We employed the heterodimeric flavoenzyme FixAB from the diazotrophic bacterium Rhodopseudomonas palustris to elucidate unique properties that underpin flavin-based electron bifurcation. FixAB is distinguished from canonical electron transfer flavoproteins (ETFs) by a second FAD that replaces the AMP of canonical ETF. We exploited near-UV–visible CD spectroscopy to resolve signals from the different flavin sites in FixAB and to interrogate the putative bifurcating FAD. CD aided in assigning the measured reduction midpoint potentials (E° values) to individual flavins, and the E° values tested the accepted model regarding the redox properties required for bifurcation. We found that the higher-E° flavin displays sequential one-electron (1-e−) reductions to anionic semiquinone and then to hydroquinone, consistent with the reactivity seen in canonical ETFs. In contrast, the lower-E° flavin displayed a single two-electron (2-e−) reduction without detectable accumulation of semiquinone, consistent with unstable semiquinone states, as required for bifurcation. This is the first demonstration that a FixAB protein possesses the thermodynamic prerequisites for bifurcating activity, and the separation of distinct optical signatures for the two flavins lays a foundation for mechanistic studies to learn how electron flow can be directed in a protein environment. We propose that a novel optical signal observed at long wavelength may reflect electron delocalization between the two flavins.en_US
dc.description.sponsorshipBiological and Electron Transfer and Catalysis (BETCy) EFRC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science (DE-SC0012518)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.titleDistinct properties underlie flavin-based electron bifurcation in a novel electron transfer flavoprotein FixAB from Rhodopseudomonas palustrisen_US
mus.citation.journaltitleJournal of Biological Chemistryen_US
mus.identifier.categoryChemical & Material Sciencesen_US
mus.identifier.categoryLife Sciences & Earth 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

Files in this item


This item appears in the following Collection(s)

Show simple item record

MSU uses DSpace software, copyright © 2002-2017  Duraspace. For library collections that are not accessible, we are committed to providing reasonable accommodations and timely access to users with disabilities. For assistance, please submit an accessibility request for library material.