BACKBONE DYNAMICS OF THE MAJOR COAT PROTEIN OF BACTERIOPHAGE M13 IN DETERGENT MICELLES BY N-15 NUCLEAR-MAGNETIC-RESONANCE RELAXATION MEASUREMENTS USING THE MODEL-FREE APPROACH AND REDUCED SPECTRAL DENSITY MAPPING
Chm. Papavoine et al., BACKBONE DYNAMICS OF THE MAJOR COAT PROTEIN OF BACTERIOPHAGE M13 IN DETERGENT MICELLES BY N-15 NUCLEAR-MAGNETIC-RESONANCE RELAXATION MEASUREMENTS USING THE MODEL-FREE APPROACH AND REDUCED SPECTRAL DENSITY MAPPING, Biochemistry, 36(13), 1997, pp. 4015-4026
The backbone dynamics of the major coat protein (gVIIIp) of the filame
ntous bacteriophage M13, solubilized in detergent micelles, have been
studied using N-15 nuclear magnetic resonance spectroscopy at three fr
equencies. Motional parameters and overall and internal correlation ti
mes were derived with the model-free approach. It was also checked whe
ther these parameters had to be modified due to anisotropic motion of
the protein/micelle complex. Reduced spectral density mapping was used
to calculate the spectral densities at J(0), J(omega(N)), and [J(omeg
a(H))]. The spectral densities were interpreted by mapping a linear or
scaled linear combination of two Lorentzians onto a J(0) - J(omega) p
lot. The major coat protein of bacteriophage M13 consists of two alpha
-helices, one of which is hydrophobic and located within the micelle,
while the other is amphipathic and located on the surface of the mice
lle. Our results indicate that the motion of the hydrophobic helix is
restricted such that it corresponds to the overall tumbling of the pro
tein/micelle complex. The interpretation of the relaxation data of the
amphipathic helix by means of the model-free approach and the reduced
spectral density mapping indicate that in addition to the overall mot
ion all residues in this helix are subject to motion on the fast nanos
econd and picosecond time scales. The motions of the vectors in the lo
w nanosecond range are characterized by similar values of the spectral
densities and correlation times and represent the motion of the amphi
pathic helix on and away from the surface of the micelle. The relaxati
on data of the residues in the hinge region connecting the helices sho
w that there is an abrupt change from highly restricted to less restri
cted motion. Both the C-terminal and N-terminal residues are very mobi
le.