Toward a Chemical Mechanism of Proton Pumping by the B-Type Cytochrome c Oxidases: Application of Density Functional Theory to Cytochrome ba[sub3] of Thermus thermophilus.
A mechanism for proton pumping by the B-type cytochrome c oxidases is presented in which one proton is pumped in conjunction with the weakly exergonic, two-electron reduction of Fe-bound O[sub2] to the Fe-Cu bridging peroxodianion and three protons are pumped in conjunction with the highly exergonic...
| Publicado en: | Journal of the American Chemical Society Vol. 130; no. 45; pp. 15002 - 15022 |
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| Autores principales: | , , |
| Formato: | Artículo |
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American Chemical Society
11/12/2008
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=35398449&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 35398449 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 11/12/2008 vid: 130 iid: 45 pid: 997 pub: American Chemical Society artinfo: ui: 35398449 10.1021/ja803112w ppf: 15002 ppct: 20 formats: tig: atl: Toward a Chemical Mechanism of Proton Pumping by the B-Type Cytochrome c Oxidases: Application of Density Functional Theory to Cytochrome ba[sub3] of Thermus thermophilus. aug: au: Fee, James A. Case, David A. Noodleman, Louis affil: Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037 su: Protons Cytochrome c Oxidases Density functionals Enzyme activation Chemical reduction Imidazoles Electrons Bilayer lipid membranes sug: subj: Protons Cytochrome c Oxidases Density functionals Enzyme activation Chemical reduction Imidazoles Electrons Bilayer lipid membranes ab: A mechanism for proton pumping by the B-type cytochrome c oxidases is presented in which one proton is pumped in conjunction with the weakly exergonic, two-electron reduction of Fe-bound O[sub2] to the Fe-Cu bridging peroxodianion and three protons are pumped in conjunction with the highly exergonic, two-electron reduction of Fe(lll)-[sup-]O-O[sup-]-Cu(ll) to form water and the active oxidized enzyme, Fe(lll)-[sup-]OH,Cu(ll). The scheme is based on the active-site structure of cytochrome ba[sub3] from Thermus the rmophllus, which is considered to be both necessary and sufficient for coupled O[sub2] reduction and proton pumping when appropriate gates are in place (not included in the model). Fourteen detailed structures obtained from density functional theory (DFT) geometry optimization are presented that are reasonably thought to occur during the four-electron reduction of O[sub2]. Each proton-pumping step takes place when a proton resides on the imidazole ring of l-His376 and the large active-site cluster has a net charge of +1 due to an uncompensated, positive charge formally associated with Cu[subB]. Four types of DFT were applied to determine the energy of each intermediate, and standard thermochemical approaches were used to obtain the reaction free energies for each step in the catalytic cycle. This application of DFT generally conforms with previously suggested criteria for a valid model (Siegbahn, P. E. M.; Blomberg, M. A. R. Chem. Rev. 2000, 100, 421-437) and shows how the chemistry of O[sub2] reduction in the heme a[sub3]-Cu[subB] dinuclear center can be harnessed to generate an electrochemical proton gradient across the lipid bilayer. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2008 holdings: @attributes: islocal: N |
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