scholarly journals Proton translocation in cytochrome c oxidase: Insights from proton exchange kinetics and vibrational spectroscopy

2015 ◽  
Vol 1847 (1) ◽  
pp. 98-108 ◽  
Author(s):  
Izumi Ishigami ◽  
Masahide Hikita ◽  
Tsuyoshi Egawa ◽  
Syun-Ru Yeh ◽  
Denis L. Rousseau
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Vibrational Spectroscopy ◽  
Proton Translocation ◽  
Proton Exchange ◽  
Exchange Kinetics

scholarly journals Limited-turnover studies on proton translocation in reconstituted cytochrome c oxidase-containing vesicles

1979 ◽  
Vol 182 (1) ◽  
pp. 149-156 ◽  
Author(s):  
R P Casey ◽  
J B Chappell ◽  
A Azzi
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Proton Pump ◽  
Proton Translocation ◽  
Strong Support ◽  
Ferrocytochrome C ◽  
Vesicle Membranes ◽  
Careful Control ◽  
Hydrogen Carrier ◽  
Reconstituted System

We have investigated ferrocytochrome c-induced proton ejection from reconstituted cytochrome c oxidase-containing vesicles using careful control of the number of enzyme turnovers. Ferrocytochrome c caused the appearance of protons at the vesicle exterior, and this could be abolished by using a protonophore. In addition, its decay was dependent on the permeability of the vesicle membranes to protons and the number of turnovers of the oxidase. These observations indicate that the ejection of protons was the result of genuine translocation. The possibility of this translocation occurring via a Mitchellian loop as a result of the presence of a reduced hydrogen carrier contaminating the enzyme was considered and excluded. Proton-translocating activity in this reconstituted system depended critically on the ratio of enzyme to lipid used in the reconstitution process and we propose a rationale to account for this. We conclude that our data provide strong support for the proposal that cytochrome c oxidase acts as a proton pump and that approx. 0.9 H+ is excluded per ferrocytochrome c molecule oxidized.

scholarly journals Water-gated mechanism of proton translocation by cytochrome c oxidase

2003 ◽  
Vol 1604 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Mårten Wikström ◽  
Michael I. Verkhovsky ◽  
Gerhard Hummer
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Proton Translocation

Cytochrome c oxidase: structure, function, and membrane topology of the polypeptide subunits

1991 ◽  
Vol 69 (9) ◽  
pp. 586-607 ◽  
Author(s):  
Chris E. Cooper ◽  
Peter Nicholls ◽  
Jo A. Freedman
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Proton Translocation ◽  
Membrane Topology ◽  
Functional Difference ◽  
Inner Mitochondrial Membrane ◽  
Physiological Control ◽  
Catalytic Core ◽  
Protein Orientation

Mitochondrial cytochrome c oxidase and its bacterial homologs catalyze electron transfer and proton translocation reactions across membranes. The eukaryotic enzyme complex consists of a large number of polypeptide subunits. Three of the subunits (I, II, and III) are mitochondrially encoded while the remaining 6 (yeast) to 10 (bovine) are nuclear encoded. Antibody and chemical-labelling experiments suggest that subunits I–III and most (but not all) of the nuclear-encoded subunits span the inner mitochondrial membrane. Subunits I and II are the catalytic core of the enzyme. Subunit I contains haem a, haem a3 and CuB, while subunit II contains CuA and the cytochrome c binding site. Subunit III and most of the nuclear subunits are essential for the assembly of a functional catalytic enzyme. Some nuclear subunits are present as isozymes, although little functional difference has yet been detected between enzyme complexes composed of different isozymes. Therefore, any additional role attributed to the nuclear-encoded subunits beyond that of enzyme assembly must be tentative. We suggest that enough evidence exists to support the idea that modification of the larger nuclear subunits (IV, V, and possibly VI) can affect enzyme turnover in vitro. Whether this is a physiological control mechanism remains to be seen.Key words: cytochrome oxidase, polypeptide subunits, antibodies, membrane protein, orientation.

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