scholarly journals Microscopic basis for kinetic gating in cytochrome c oxidase: insights from QM/MM analysis

2015 ◽  
Vol 6 (1) ◽  
pp. 826-841 ◽  
Author(s):  
Puja Goyal ◽  
Shuo Yang ◽  
Qiang Cui
Keyword(s):  
Cytochrome C ◽  
Proton Transfer ◽  
Cytochrome C Oxidase ◽  
Proton Pumping ◽  
Kinetic Features

Understanding the mechanism of vectorial proton pumping in biomolecules requires establishing the microscopic basis for the regulation of both thermodynamic and kinetic features of the relevant proton transfer steps.

scholarly journals Proton-transfer pathways in the mitochondrial S. cerevisiae cytochrome c oxidase

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Markus L. Björck ◽  
Jóhanna Vilhjálmsdóttir ◽  
Andrew M. Hartley ◽  
Brigitte Meunier ◽  
Linda Näsvik Öjemyr ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Proton Transfer ◽  
Cytochrome C Oxidase ◽  
Proton Pumping ◽  
Heart Mitochondria ◽  
Negative Side ◽  
Bovine Heart ◽  
Proton Uptake ◽  
Mammalian Counterpart ◽  
Kinetics Of

AbstractIn cytochrome c oxidase (CytcO) reduction of O2 to water is linked to uptake of eight protons from the negative side of the membrane: four are substrate protons used to form water and four are pumped across the membrane. In bacterial oxidases, the substrate protons are taken up through the K and the D proton pathways, while the pumped protons are transferred through the D pathway. On the basis of studies with CytcO isolated from bovine heart mitochondria, it was suggested that in mitochondrial CytcOs the pumped protons are transferred though a third proton pathway, the H pathway, rather than through the D pathway. Here, we studied these reactions in S. cerevisiae CytcO, which serves as a model of the mammalian counterpart. We analyzed the effect of mutations in the D (Asn99Asp and Ile67Asn) and H pathways (Ser382Ala and Ser458Ala) and investigated the kinetics of electron and proton transfer during the reaction of the reduced CytcO with O2. No effects were observed with the H pathway variants while in the D pathway variants the functional effects were similar to those observed with the R. sphaeroides CytcO. The data indicate that the S. cerevisiae CytcO uses the D pathway for proton uptake and presumably also for proton pumping.

scholarly journals The mechanism of proton translocation by the cytochrome system of mitochondria. Characterization of proton-transfer reactions associated with oxidoreductions of terminal respiratory carriers

1983 ◽  
Vol 216 (2) ◽  
pp. 259-272 ◽  
Author(s):  
S Papa ◽  
F Guerrieri ◽  
G Izzo
Keyword(s):  
Cytochrome C ◽  
Proton Transfer ◽  
Cytochrome C Oxidase ◽  
Electron Flow ◽  
Aerobic Oxidation ◽  
Proton Pumping ◽  
Rat Liver Mitochondria ◽  
Complex Scalar ◽  
Total Electron ◽  
Ionizable Groups

A direct kinetic analysis is presented of rapid proton-releasing reactions at the outer or C-side of the membrane, in ox heart and rat liver mitochondria, associated with aerobic oxidation of reduced terminal respiratory carriers in the presence of antimycin. Valinomycin plus K+ enhances the rate of cytochrome c oxidation and the rate and extent of H+ release. In the presence of valinomycin the leads to H+/e- ratio, computed on the basis of total electron flow from respiratory carriers to oxygen, varies with pH, remaining always lower than 1, and is unaffected by N-ethylmaleimide. 2-Heptyl-4-hydroxyquinoline N-oxide and 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole, at concentrations which inhibit in the presence of antimycin the oxygen-induced reduction of b cytochromes, cause also a marked depression of the H+ release associated with aerobic oxidation of terminal respiratory carriers. Aerobic oxidation of the cytochrome system in mitochondria and of isolated b-c1 complex and cytochrome c oxidase results in scalar proton release from ionizable groups (redox Bohr effects). In mitochondria and submitochondrial particles, about 70% of the oxidoreductions of the components of the cytochrome system are linked to scalar proton transfer by ionizable groups. In isolated b-c1 complex scalar proton transfer, resulting from redox Bohr effect, amounts to 0.9H+ per Fe-S protein (190 muT). In isolated cytochrome c oxidase, Bohr protons amount to 0.8 per haem a + a3. The results presented indicate that the H+ release from mitochondria during oxidation of terminal respiratory carriers derives from residual antimycin-insensitive electron flow in the quinone-cytochrome c span and from redox Bohr effects in the b-c1 complex and cytochrome c oxidase. There is no sign of proton pumping by cytochrome oxidase during its transition from the reduced to the active ‘pulsed’ state and the first one or two turnovers.

Molecular architecture of the proton diode of cytochrome c oxidase

2008 ◽  
Vol 36 (6) ◽  
pp. 1169-1174 ◽  
Author(s):  
Peter Brzezinski ◽  
Joachim Reimann ◽  
Pia Ädelroth
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Proton Transfer ◽  
Cytochrome C Oxidase ◽  
Proton Translocation ◽  
Short Review ◽  
Proton Pumping ◽  
Molecular Architecture ◽  
Electrochemical Gradient ◽  
Membrane Bound

CytcO (cytochrome c oxidase) is a membrane-bound multisubunit protein which catalyses the reduction of O2 to H2O. The reaction is arranged topographically so that the electrons and protons are taken from opposite sides of the membrane and, in addition, it is also linked to proton pumping across the membrane. Thus the CytcO moves an equivalent of two positive charges across the membrane per electron transferred to O2. Proton transfer through CytcO must be controlled by the protein to prevent leaks, which would dissipate the proton electrochemical gradient that is maintained across the membrane. The molecular mechanism by which the protein controls the unidirectionality of proton-transfer (cf. proton diode) reactions and energetically links electron transfer to proton translocation is not known. This short review summarizes selected results from studies aimed at understanding this mechanism, and we discuss a possible mechanistic principle utilized by the oxidase to pump protons.

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