Changes in Rhodospirillum rubrum cytochrome c/sub 2/ and subsequent renaturation: An /sup 15/N NMR study
The /sup 15/N-enriched ferrocytochrome c/sub 2/from Rhodospirillum rubrum was studied by /sup 15/N NMR at different solvent pH values. The mobility and chemical shift to the N-terminal glutamic acid (335.4 ppm at pH 5.1) were found to depend on pH. It was least mobile between pH 8 and 9.0, which is explained in terms of pH-dependent conformational changes and formation of salt linkages and/or hydrogen bonds. The resonances of the lysine side chains are centered around 341.7 ppm at low pH and move upfield with pH by about 8.4 ppm with pH/sub a/ values of 10.8. The exchange rates of the epsilonNH protons are lowest near the pK/sub a/ values. The protein is very stable in the pH range between 4.9 and 10.0 but unfolds abruptly at pH 10.5-11. Denaturation was verified by the measurement of several parameters by NMR. The renaturation of the protein demonstrates that the folding begins with reformation of home coordination and establishment of a hydrophobic core, followed by positioning of side chains and peptide backbones linking the nucleation centers. The repositioning processes had time scales of minutes to hours in contrast to the reported values of seconds in some studies.
- Research Organization:
- Univ. of California, Davis (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6401008
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 85:9
- Country of Publication:
- United States
- Language:
- English
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CYTOCHROMES
NUCLEAR MAGNETIC RESONANCE
RHODOSPIRILLUM
PROTEIN DENATURATION
CONFORMATIONAL CHANGES
NITROGEN 15
NMR SPECTRA
PH VALUE
BACTERIA
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PIGMENTS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics