Padmanabhan S, Baldwin R L
Department of Biochemistry, Beckman Center, Stanford University Medical School, California 94305-5307.
Protein Sci. 1994 Nov;3(11):1992-7. doi: 10.1002/pro.5560031111.
Straight-chain, non-natural, nonpolar amino acids norleucine, norvaline, and alpha-amino-n-butyric acid at various spacings do not interact with themselves to stabilize helix formation in alanine-based peptides, but do interact with a Tyr spaced i, i + 4 to stabilize alanine helices, similar to the helix-stabilizing i, i + 4 Tyr-Leu and Tyr-Val interactions reported earlier (Padmanabhan S, Baldwin RL, 1994, J Mol Biol 241:706-713). Leu spaced i, i + 4 from another Leu is measurably helix-stabilizing relative to the corresponding i, i + 3 pair, but less so than for i, i + 4 Val-Leu, Ile-Leu, or Phe-Leu pairs (relative to the corresponding i, i + 3 pairs) when Leu is C-terminal to the other nonpolar amino acid. Our results indicate that limited side-chain flexibility in an alpha-helix strongly favors the interaction between 2 nonpolar residues to stabilize an isolated alpha-helix.
直链、非天然、非极性氨基酸正亮氨酸、正缬氨酸和α-氨基正丁酸在不同间距时，自身之间不会相互作用以稳定基于丙氨酸的肽中的螺旋形成，但与间隔为i、i + 4的酪氨酸相互作用时，会稳定丙氨酸螺旋，这与之前报道的稳定螺旋的i、i + 4酪氨酸-亮氨酸和酪氨酸-缬氨酸相互作用类似（Padmanabhan S，Baldwin RL，1994，《分子生物学杂志》241:706 - 713）。相对于相应的i、i + 3对，当亮氨酸位于另一个非极性氨基酸的C末端时，与另一个亮氨酸间隔为i、i + 4的亮氨酸可测量地稳定螺旋，但比i、i + 4缬氨酸-亮氨酸、异亮氨酸-亮氨酸或苯丙氨酸-亮氨酸对（相对于相应的i、i + 3对）的稳定作用小。我们的结果表明α-螺旋中有限的侧链柔韧性强烈有利于两个非极性残基之间的相互作用，以稳定孤立的α-螺旋。
