C-terminal capping motifs in model helical peptides |
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Authors: | Kallenbach N R Gong Y |
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Institution: | Department of Chemistry, New York University, NY 10003, USA. kallnbch@is.nyu.edu |
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Abstract: | Solution structures of a series of consensus sequence peptides with N- and C-terminal capping interactions have been determined by 2-D nuclear magnetic resonance spectroscopy and a simulated annealing strategy. All peptides are found to be stabilized by a hydrophobic interaction and a capping box structure (SXXE) at the N-terminus whereas several different capping motifs are discerned near the peptide C-terminus. Among these, the asparagine side chain-backbone main chain (i, i-4) capping structure is most stabilizing and highly populated in the simulated annealing calculation. A glycine alphaL capping motif stabilizes the peptide terminus, which otherwise tends to fray, but this is occupied only a fraction of the time in the trial structures determined. Our experimental search over several models for a second type of C-terminal capping structure, the so-called 'Schellman motif', which is seen in native proteins, is unsuccessful, indicating this structural element contributes less to oligopeptide stability in solution and most probably populates only transiently. |
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