Groebke K, Renold P, Tsang K Y, Allen T J, McClure K F, Kemp D S
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA.
Proc Natl Acad Sci U S A. 1996 Apr 30;93(9):4025-9. doi: 10.1073/pnas.93.9.4025.
The helicity in water has been determined for several series of alanine-rich peptides that contain single lysine residues and that are N-terminally linked to a helix-inducing and reporting template termed Ac-Hel1. The helix-propagating constant for alanine (sAla value) that best fits the properties of these peptides lies in the range of 1.01-1.02, close to the value reported by Scheraga and coworkers [Wojcik, J., Altmann, K.-H. & Scheraga, H.A. (1990) Biopolymers 30, 121-134], but significantly lower than the value assigned by Baldwin and coworkers [Chakrabartty, A., Kortemme, T. & Baldwin, R.L. (1994) Protein Sci. 3,843-852]. From a study of conjugates Ac-Hel1-Ala(n)-Lys-Ala(m)-NH2 and analogs in which the methylene portion of the lysine side chain is truncated, we find that the unusual helical stability of Ala(n)Lys peptides is controlled primarily by interactions of the lysine side chain with the helix barrel, and only passively by the alanine matrix. Using 1H NMR spectroscopy, we observe nuclear Overhauser effect crosspeaks consistent with proton-proton contacts expected for these interactions.
已测定了几组富含丙氨酸的肽在水中的螺旋度，这些肽含有单个赖氨酸残基，且在N端与一个称为Ac-Hel1的螺旋诱导和报告模板相连。最符合这些肽特性的丙氨酸螺旋传播常数（sAla值）在1.01 - 1.02范围内，接近Scheraga及其同事报道的值[Wojcik, J., Altmann, K.-H. & Scheraga, H.A. (1990) Biopolymers 30, 121 - 134]，但显著低于Baldwin及其同事所确定的值[Chakrabartty, A., Kortemme, T. & Baldwin, R.L. (1994) Protein Sci. 3, 843 - 852]。通过对共轭物Ac-Hel1-Ala(n)-Lys-Ala(m)-NH2及其赖氨酸侧链亚甲基部分被截短的类似物的研究，我们发现Ala(n)Lys肽异常的螺旋稳定性主要由赖氨酸侧链与螺旋桶的相互作用控制，而丙氨酸基质仅起被动作用。使用1H NMR光谱，我们观察到与这些相互作用预期的质子 - 质子接触一致的核Overhauser效应交叉峰。
