| Autor: |
Millhauser, Glenn L., Stenland, Chris J., Hanson, Paul, Bolin, Kimberly A., van de Ven, Frank J.M. |
| Zdroj: |
JMB Online (Journal of Molecular Biology); April 11, 1997, Vol. 267 Issue: 4 p963-974, 12p |
| Abstrakt: |
Recent experimental and theoretical work suggests that alanine-rich peptides fold as a mixture of 310-helix (i → i + 3 hydrogen bonding) and α-helix (i → i + 4 hydrogen bonding). In order to assess the relative proportions of the two conformers, NMR studies were performed on the 16 residue sequences: Ac-AAAAKAAAAKAAAAKA-NH2(3K) and Ac-AMAAKAWAAKAAAARA-NH2(MW). Hydrogen/deuterium-exchange kinetics measured for the first three amide protons of the 3K peptide indicate that the NH of Ala3 is partially protected from exchange. This result is consistent with the presence of an i → i + 3 hydrogen bond between the carbonyl group of the acetyl blocking group and the NH group of Ala3. The MW peptide is a modified version of the 3K peptide, designed to increase αH signal dispersion.1H NMR spectra of the MW peptide at 750 MHz reveal a series of intermediate range (NOEs) consistent with a mixture of 310-helix and α-helix. The relative intensities of the αN(i,i + 3) and αβ(i, i + 3) (nuclear Overhauser enhancements) NOEs suggest that 310-helix is present throughout the peptide, but with the greatest contribution at the termini. A model was developed to determine the relative contributions of 310-helix and α-helix. Lower bounds for the population of 310-helix are approximately 50% at the termini and 25% in the middle of the peptide. The greatest α-helical content is between the middle of the peptide and the N terminus. |
| Databáze: |
Supplemental Index |
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