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Laue diffraction study on the structure of cytochrome c peroxidase compound I
V Fülöp1, R P Phizackerley, S M Soltis
1Oxford Centre for Molecular Sciences, UK.
Structure (London, England : 1993)
|March 15, 1994
Summary
Yeast cytochrome c peroxidase forms a transient intermediate, compound I, containing a free radical and oxyferryl heme. Structural analysis reveals minimal changes at the radical site, suggesting efficient electron transfer evolution.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Yeast cytochrome c peroxidase is a mitochondrial enzyme protecting against peroxides.
- It contains a heme group and plays a role in the electron transport chain.
- A transient intermediate, compound I, forms during its reaction with hydrogen peroxide.
Purpose of the Study:
- To determine the reliable structure of the doubly oxidized transient intermediate (compound I).
- To investigate the structural changes associated with compound I formation.
- To understand the role of Trp191 and the oxyferryl heme group.
Main Methods:
- Production of compound I in crystalline yeast cytochrome c peroxidase using a flow cell.
- Monitoring the reaction with microspectrophotometry and Laue crystallography.
- Structure determination of compound I using Laue diffraction data processed with the LEAP software package.
Main Results:
- Achieved nearly complete conversion to compound I within two minutes.
- Observed clear structural changes at the peroxide-binding site.
- Found no significant structural changes at the Trp191 radical site.
Conclusions:
- The heme environment geometry allows for minimal structural adjustments during electron transfer.
- These structural adaptations are comparable to the Fe2+/Fe3+ transition in cytochrome c.
- Enzymes like cytochrome c peroxidase have evolved for efficient electron transfer with minimal conformational changes.