Effects of Protein Structure on Iron–Polypeptide Vibrational Dynamic Coupling in Cytochrome c
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemistry; Penn State, Erie, PA (United States). Behrend College
- Univ. of Rochester, NY (United States). Dept. of Chemistry
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemistry
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Cytochrome c (Cyt c) has a heme covalently bound to the polypeptide via a Cys-X-X-Cys-His (CXXCH) linker that is located in the interface region for protein-protein interactions. To determine whether the polypeptide matrix influences iron vibrational dynamics, nuclear resonance vibrational spectroscopy (NRVS) measurements were performed on Fe-57-labeled ferric Hydrogenobacter thermophilus cytochrome c-552, and variants M13V, M13V/K22M, and A7F, which have structural modifications that alter the composition or environment of the CXXCH pentapeptide loop. Simulations of the NRVS data indicate that the 150-325 cm(-1) region is dominated by N-His-Fe-S-Met axial ligand and polypeptide motions, while the 325-400 cm(-1) region shows dominant contributions from nu(Fe-N-Pyr) (Pyr = pyrrole) and other heme-based modes. Diagnostic spectral signatures that directly relate to structural features of the heme active site are identified using a quantum chemistry-centered normal coordinate analysis (QCC-NCA). In particular, spectral features that directly correlate with CXXCH loop stiffness, the strength of the Fe-His interaction, and the degree of heme distortion are identified. Cumulative results from our investigation suggest that compared to the wild type (wt), variants M13V and M13V/K22M have a more rigid CXXCH pentapeptide segment, a stronger Fe-N-His interaction, and a more ruffled heme. Conversely, the A7F variant has a more planar heme and a weaker Fe-N-His bond. These results are correlated to the observed changes in reduction potential between wt protein and the variants studied here. Implications of these results for Cyt c biogenesis and electron transfer are also discussed.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Institutes of Health (NIH); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- R01-GM63170; AC02-06CH11357
- OSTI ID:
- 1261133
- Alternate ID(s):
- OSTI ID: 1362102
- Journal Information:
- Biochemistry, Vol. 54, Issue 4; ISSN 0006-2960
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
What Can Be Learned from Nuclear Resonance Vibrational Spectroscopy: Vibrational Dynamics and Hemes
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journal | September 2017 |
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