These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Characterization of electron-transfer and proton-translocation activities in bovine heart mitochondrial cytochrome c oxidase deficient in subunit III.
    Author: Prochaska LJ, Reynolds KA.
    Journal: Biochemistry; 1986 Feb 25; 25(4):781-7. PubMed ID: 3008812.
    Abstract:
    The electron-transfer and proton-translocation activities of cytochrome c oxidase deficient in subunit III (Mr 29 884) prepared by native gel electrophoresis [Ludwig, B., Downer, N. W., & Capaldi, R. A. (1979) Biochemistry 18, 1401-1407] have been investigated. This preparation has been depleted of 82-87% of its subunit III content as quantitated by Coomassie Brilliant Blue staining intensity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and [14C]dicyclohexylcarbodiimide labeling. The maximum rate of electron transfer of the subunit III deficient enzyme at pH 6.5 is 383 s-1, 78% of control enzyme. Neither the high-affinity site (Km = 10(-8) M) nor the low-affinity site (Km = 10(-6) M) of the cytochrome c kinetic interaction with cytochrome c oxidase is affected by the removal of subunit III. Subunit III deficient cytochrome c oxidase retains the ability to bind cytochrome c in both the high- and low-affinity sites as determined in direct thermodynamic binding experiments. Liposomes containing this preparation exhibit a respiratory control ratio [Hinkle, P. C., Kim, J. J., & Racker, E. (1972) J. Biol. Chem. 247, 1338-1341] of 3.9, while liposomes containing control enzyme exhibit a ratio of 4.3, suggesting that they have a similar proton permeability. Vectorial proton translocation initiated by the addition of ferrocytochrome c in liposomes containing subunit III deficient enzyme is decreased by 64% compared to those containing control enzyme. When the proton-translocated to electron-transferred ratio is measured in these phospholipid vesicles at constant enzyme turnover, removal of subunit III from the enzyme decreases the ratio from 0.52 to 0.21, a 60% decrease.(ABSTRACT TRUNCATED AT 250 WORDS)
    [Abstract] [Full Text] [Related] [New Search]