Bruch M D, Dhingra M M, Gierasch L M
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
Proteins. 1991;10(2):130-9. doi: 10.1002/prot.340100206.
Recently, Presta and Rose proposed that a necessary condition for helix formation is the presence of residues at the N- and C-termini (called NTBs and CTBs) whose side chains can form hydrogen bonds with the initial four amides and the last four carbonyls of the helix, which otherwise lack intrahelical hydrogen bonding partners. We have tested this hypothesis by conformational analysis by circular dichroism (CD) of a synthetic peptide corresponding to a region (171-188) of the protein carboxypeptidase A; in the protein, residues 174 to 186 are helical and are flanked by NTBs and CTBs. Since helix formation in this peptide may also be stabilized by electrostatic interactions, we have compared the helical content of the native peptide with that of several modified peptides designed to enable dissection of different contributions to helix stability. As expected, helix dipole interactions appear to contribute substantially, but we conclude that hydrogen bonding interactions as proposed by Presta and Rose also stabilize helix formation. To assist in comparison of different peptides, we have introduced two concentration-independent CD parameters which are sensitive probes of helix formation.
最近，普雷斯塔和罗斯提出，螺旋形成的一个必要条件是在N端和C端存在残基（称为NTB和CTB），其侧链可以与螺旋的最初四个酰胺和最后四个羰基形成氢键，否则这些螺旋缺乏螺旋内氢键伙伴。我们通过对一种对应于蛋白质羧肽酶A区域（171 - 188）的合成肽进行圆二色性（CD）构象分析来检验这一假设；在该蛋白质中，174至186位残基呈螺旋状，两侧为NTB和CTB。由于该肽中的螺旋形成也可能通过静电相互作用得以稳定，我们将天然肽的螺旋含量与几种经过修饰的肽进行了比较，这些修饰肽旨在剖析对螺旋稳定性的不同贡献。正如预期的那样，螺旋偶极相互作用似乎起到了很大作用，但我们得出结论，普雷斯塔和罗斯提出的氢键相互作用也能稳定螺旋的形成。为了便于比较不同的肽，我们引入了两个与浓度无关的CD参数，它们是螺旋形成的敏感探针。
