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X-ray absorption spectroscopy of oriented cytochrome oxidase
G N George1, S P Cramer, T G Frey
1Exxon Research and Engineering Co., Annandale, NJ.
Biochimica Et Biophysica Acta
|May 6, 1993
Summary
This study examined copper, iron, and zinc in mitochondrial cytochrome oxidase using polarized X-ray absorption. Findings reveal specific copper orientations and a copper-thioether interaction at the CuA site within the enzyme.
Area of Science:
- Biophysics
- Biochemistry
- Structural Biology
Background:
- Mitochondrial cytochrome oxidase is crucial for cellular respiration.
- Understanding the precise structure and metal coordination is key to its function.
Purpose of the Study:
- To investigate the structural and orientational properties of metal centers (copper, iron, zinc) in mitochondrial cytochrome oxidase.
- To elucidate the coordination environment of the copper ions (CuA and CuB) and the binuclear site (heme a3).
Main Methods:
- Polarized X-ray absorption spectroscopy (XAS) was employed.
- Experiments were conducted on oriented membrane multilayers of the enzyme.
Main Results:
- Tetragonal copper (CuB) was identified, oriented roughly perpendicular to the membrane normal.
- A long Cu-S or Cu-Cl interaction (2.6 Å) was observed, assigned to copper-thioether coordination at the CuA site, oriented along the membrane normal.
- The coordination of zinc, iron, and the CuB heme a3 binuclear site was analyzed.
Conclusions:
- The study provides detailed structural insights into the metal centers of cytochrome oxidase.
- Specific orientations and coordination bonds were determined, contributing to a better understanding of electron transfer pathways.