| Autor: |
YOUNG, JOHN K., MARí, FRANK, XU, MINZHEN, HUMPHREYS, ROBERT E., CLEMENTE, NIKKI M., STATTEL, JAMES M., NELSON, DONALD J., GAMBINO, JOSEPH, WRIGHT, GEORGE E. |
| Zdroj: |
Journal of Peptide Research; 1997, Vol. 50 Issue 2, p122-131, 10p |
| Abstrakt: |
The H NMR-determined structure and dynamics of a synthetic, amphiphilic α-helical peptide, PH-1.0 (LYQELQKLTQTLK), and several homologs were compared in 50% trifluoroethanol-d2 (TFE-d2)/H2O and in sodium dodecyW25 sulfate (SDS-d25) micelles. The peptides were designed to test the influence on secondary structure of placement of favored and disfavored residues relative to a 'longitudinal, hydrophobic strip-of-helix' defined by the repeating leucines. PH-1.0 was highly ordered as an α-helix in 50% TFE-d2/H2O and in SDS-d25 micelles. Homologs PH-1.1, in which LI was replaced by T, and PH-1.4, in which LI 2 was replaced by T, were found to be partially helical in both media. Calculated structures in SDS-d25 revealed that the helix of PH-1.1 was slightly disordered at the N-terminus, but that of PH-1.4 was completely disordered at the C-terminus. Examination of distributions of hydrophobic residues in protein structures revealed that, when ♦= LIVFM and ⋄= nonLIVFM, the pattern ⋄♦♦⋄⋄ is favored and ⋄♦⋄♦⋄ is disfavored in α-helices. Several analogs of PH-1.0 incorporating these patterns were studied. Peptide PH-1.12 ( LYQE LQK L LQT LK) retained a-helical structure in both 50% TFE-d2/H2O and in SDS-d25 micelles. However, although PH-1.13 ( LYQE LQK L LQT LK) was fully helical in 50% TFE, it was helical only through residue 6 in SDS micelles. Two homologs containing an additional loop of the helix and repeats of favored (PH-5.0, NY LQT L LET LKT L LQK) or suppressed LL patterns (PH-5.11, NY LQT LE LT LK LT LQK) gave similar results, i.e. the latter peptide was helical only through residue 6 in SDS micelles. The degree of local order in these SDS micelle-adsorbed peptides correlates to placement of hydrophobic residues in motifs which are favored or disfavored in proteins in general and in α-helices specifically. © Munksgaard 1997. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Plný text