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Internal motional amplitudes and correlated bond rotations in an α‐helical peptide derived from 13 C and 15 N NMR relaxation
Author(s) -
Idiyatullin Djaudat,
Krushelnitsky Alexei,
Nesmelova Irina,
Daragan Vladimir A.,
Mayo Kevin H.,
Blanco Francesco,
Serrano Luis
Publication year - 2000
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.9.11.2118
Subject(s) - chemistry , crystallography , side chain , steric effects , relaxation (psychology) , rotational diffusion , helix (gastropod) , stereochemistry , dipole , molecule , psychology , social psychology , ecology , organic chemistry , snail , biology , polymer
Peptide GFSKAELAKARAAKRGGY folds in an α‐helical conformation that is stabilized by formation of a hydrophobic staple motif and an N‐terminal capping box (Munoz V, Blanco FJ, Serrano L, 1995, Struct Biol 2 :380–385). To investigate backbone and side‐chain internal motions within the helix and hydrophobic staple, residues F2, A5, L7, A8, and A10 were selectively 13 C‐ and 15 N‐enriched and NMR relaxation experiments were performed in water and in water/trifluoroethanol (TFE) solution at four Larmor frequencies (62.5, 125, 150, and 200 MHz for 13 C). Relaxation data were analyzed using the model free approach and an anisotropic diffusion model. In water, angular variances of motional vectors range from 10 to 20° and backbone ϕ,ψ bond rotations for helix residues A5, L7, A8, and A10 are correlated indicating the presence of C α ‐H, C α ‐C β , and N‐H rocking‐type motions along the helix dipole axis. L7 side‐chain C β H 2 and C γ H motions are also correlated and as motionally restricted as backbone C α H, suggesting considerable steric hindrance with neighboring groups. In TFE which stabilizes the fold, internal motional amplitudes are attenuated and rotational correlations are increased. For the side chain of hydrophobic staple residue F2, wobbling‐in‐a‐cone type motions dominate in water, whereas in TFE, the C β ‐C γ bond and phenyl ring fluctuate more simply about the C α ‐C β bond. These data support the Daragan‐Mayo model of correlated bond rotations (Daragan VA, Mayo KH, 1996, J Phys Chem 100 :8378–8388) and contribute to a general understanding of internal motions in peptides and proteins.