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Hydrogen exchange in Pseudomonas cytochrome c-551
R Timkovich1, L A Walker, M Cai
1Department of Chemistry, University of Alabama, Tuscaloosa 35487-0336.
Biochimica Et Biophysica Acta
|May 22, 1992
Summary
Hydrogen exchange rates reveal structural stability in ferrocytochrome c-551. Specific amino acid clusters, including Ile-48/Lys-49 and Leu-74/Ala-75/Lys-76/Val-78, exhibit the slowest amide proton exchange, indicating key structural roles.
Area of Science:
- Biochemistry
- Structural Biology
- Protein Dynamics
Background:
- Ferrocytochrome c-551 from Pseudomonas aeruginosa is a small hemeprotein involved in electron transport.
- Understanding protein stability and dynamics is crucial for elucidating protein function.
Purpose of the Study:
- To measure and estimate hydrogen exchange rates for amide protons in ferrocytochrome c-551.
- To identify regions of structural stability within the protein.
Main Methods:
- 1H-NMR spectroscopy was employed to monitor hydrogen-deuterium exchange.
- Methods included direct observation of proton intensity decrease and saturation transfer from solvent water.
- Measurements were conducted at neutral pH and 300 K.
Main Results:
- Hydrogen exchange rates for 75 out of 82 amide protons were determined, spanning eight orders of magnitude.
- Heme ligand and thioether bridge residues showed slow exchange.
- The slowest exchanging amide protons were localized in two clusters: Ile-48/Lys-49 (40's helix) and Leu-74/Ala-75/Lys-76/Val-78 (C-terminal alpha helix).
Conclusions:
- The identified clusters of slowly exchanging amide protons represent regions of high structural stability in ferrocytochrome c-551.
- These stable regions likely play significant roles in maintaining the protein's overall structure and function.