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Functional binding of cardiolipin to cytochrome c oxidase

N C Robinson1

  • 1Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.

Journal of Bioenergetics and Biomembranes
|April 1, 1993
PubMed

Insights

Bovine cytochrome c oxidase requires tightly bound cardiolipin for full electron transport activity. This study quantifies cardiolipin binding and its crucial role in enzyme function.

Area of Science:

  • Biochemistry
  • Mitochondrial respiration

Background:

  • Bovine cytochrome c oxidase (aa3) contains 3-4 tightly bound cardiolipin molecules.
  • At least two cardiolipin molecules are essential for optimal electron transport activity.

Purpose of the Study:

  • To investigate the functional significance of cardiolipin binding to bovine cytochrome c oxidase.
  • To quantify the binding affinity of cardiolipin and its analogues to the enzyme.

Main Methods:

  • Assessing electron transport activity restoration in the presence of cardiolipin and analogues.
  • Direct binding measurements using radiolabeled cardiolipin ([14C]-acetyl-cardiolipin).
  • Enzyme solubilization using dodecyl maltoside and Triton X-100 detergents.

Main Results:

  • Cytochrome c oxidase activity drops to 40-50% without tightly bound cardiolipin.
  • Functional binding constants (Kd,app) for cardiolipin were determined to be approximately 1 microM.
  • Direct binding assays indicated a high affinity (Kd < 0.1 microM) for cardiolipin when solubilized with Triton X-100.

Conclusions:

  • Cardiolipin plays a critical role in maintaining the full catalytic activity of bovine cytochrome c oxidase.
  • The binding affinity of cardiolipin to cytochrome c oxidase is significant and essential for its function.
  • These findings contribute to understanding cardiolipin's association with mitochondrial electron transport complexes.

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