Protein Science, Vol 7, Issue 3 720-729, Copyright © 1998 by Cold Spring Harbor Laboratory Press

ARTICLE

Motional dynamics of residues in a {beta}-hairpin peptide measured by (13)C-NMR relaxation

M. RAMIREZ-ALVARADO, V. A. DARAGAN, L. SERRANO and K. H. MAYO
Department of Biochemistry, Biomedical Engineering Center, University of Minnesota, Minneapolis, Minnesota 55455 European Molecular Biology Laboratory, Structures and Biocomputing Programme, Meyerhofstra{szlig}e 1, 69012 Heidelberg, Germany

Structurally characterizing partially folded peptides is problematic given the nature of their transient conformational states. (13)C-NMR relaxation data can provide information on the geometry of bond rotations, motional restrictions, and correlated bond rotations of the backbone and side chains and, therefore, is one approach that is useful to assess the presence of folded structure within a conformational ensemble. A peptide 12mer, R(1)GITVNG(7)KTYGR(12), has been shown to partially fold in a relatively stable {beta}-hairpin conformation centered at NG. Here, five residues, G2, V5, G7, Y10, G11, were selectively (13)C-enriched, and (13)C-NMR relaxation experiments were performed to obtain auto- and cross-correlation motional order parameters, correlation times, bond rotation angular variances, and bond rotational correlation coefficients. Our results indicate that, of the three glycines, G7 within the hairpin {beta}-turn diplays the most correlated {phi}(t),{psi}(t) rotations with its axis of rotation bisecting the angle defined by the H-C-H bonds. These positively correlated bond rotations give rise to ``twisting'' type motions of the HCH group. V5 and Y10 {phi},{psi} bond rotations are also positively correlated, with their C({beta})C({alpha})H groups undergoing similar ``twisting'' type motions. Motions of near-terminal residues G2 and G11 are less restricted and less correlated and are best described as wobbling-in-a-cone. V5 and Y10 side-chain motions, aside from being highly restricted, were found to be correlated with {phi},{psi} bond rotations. At 303 K, where the hairpin is considered ``unfolded,'' the peptide exists in a transient, collapsed state because backbone and side-chain motions of V5, G7, and Y10 remain relatively restricted, unlike their counterparts in GXG-based tripeptides. These results provide unique information toward understanding conformational variability in the unfolded state of proteins, which is necessary to solve the protein folding problem.
CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				V. A. Goehlert, E. Krupinska, L. Regan, and M. J. Stone Analysis of side chain mobility among protein G B1 domain mutants with widely varying stabilities Protein Sci., December 1, 2004; 13(12): 3322 - 3330. [Abstract] [Full Text] [PDF]

				D. Idiyatullin, I. Nesmelova, V. A. Daragan, and K. H. Mayo Comparison of 13C{alpha}H and 15NH backbone dynamics in protein GB1 Protein Sci., May 1, 2003; 12(5): 914 - 922. [Abstract] [Full Text] [PDF]