NMR Characterization of a Peptide Model Provides Evidence for Significant Structure in the Unfolded State of the Villin Headpiece Helical Subdomain
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- 作者：Yuefeng Tang ; Michael J. Goger ; and Daniel P. Raleigh
- 刊名：Biochemistry
- 出版年：2006
- 出版时间：June 6, 2006
- 年：2006
- 卷：45
- 期：22
- 页码：6940 - 6946
- 全文大小：369K
- 年卷期：v.45,no.22(June 6, 2006)
- ISSN：1520-4995
文摘
The villin headpiece subdomain (HP36) is the smallest naturally occurring protein that foldscooperatively. The protein folds on a microsecond time scale. Its small size and very rapid folding havemade it a popular target for biophysical studies of protein folding. Temperature-dependent one-dimensional(1D) NMR studies of the full-length protein together with CD and 1D NMR studies of the 21-residuepeptide fragment (HP21) derived from HP36 have shown that there is significant structure in the unfoldedstate of HP36 and have demonstrated that HP21 is a good model of these interactions. Here, wecharacterized the model peptide HP21 in detail by two-dimensional NMR. Strongly upfield shifted C
protons, the magnitude of the 3JNH, coupling constants, and the pattern of backbone-backbone andbackbone-side chain NOEs indicate that the ensemble of structures populated by HP21 contains -helicalstructure and native as well as non-native hydrophobic contacts. The hydrogen-bonded secondary structureinferred from the NOEs is, however, not sufficient to confer significant protection against amide H-Dexchange. These studies indicate that there is significant secondary structure and hydrophobic clusteringin the unfolded state of HP36. The implications for the folding of HP36 are discussed.
protons, the magnitude of the 3JNH, coupling constants, and the pattern of backbone-backbone andbackbone-side chain NOEs indicate that the ensemble of structures populated by HP21 contains -helicalstructure and native as well as non-native hydrophobic contacts. The hydrogen-bonded secondary structureinferred from the NOEs is, however, not sufficient to confer significant protection against amide H-Dexchange. These studies indicate that there is significant secondary structure and hydrophobic clusteringin the unfolded state of HP36. The implications for the folding of HP36 are discussed.