von Heijne G
Department of Molecular Biology, Karolinska Institute Center for Biotechnology, Huddinge, Sweden.
J Mol Biol. 1991 Apr 5;218(3):499-503. doi: 10.1016/0022-2836(91)90695-3.
Integral membrane proteins often contain proline residues in their presumably alpha-helical transmembrane segments. This is in marked contrast to globular proteins, where proline is rarely found inside alpha-helices. Proline residues cause kinks in helices, and, in addition to leaving the i-4 backbone carbonyl without its normal hydrogen bond donor, also sterically prevent the (i-3)-carbonyl-(i + l)-amide backbone hydrogen bond from forming. Here, some structural aspects of proline kinks in transmembrane helices are discussed on the basis of an analysis of Pro-kinked helices in the photosynthetic reaction center and bacteriorhodopsin, as well as results from an analysis of Pro-containing transmembrane segments identified in the NBRF Protein Sequence Databank.
整合膜蛋白在其推测为α螺旋的跨膜区段中常常含有脯氨酸残基。这与球状蛋白形成显著对比，在球状蛋白中，脯氨酸很少出现在α螺旋内部。脯氨酸残基会导致螺旋出现扭结，并且，除了使i-4位主链羰基失去其正常的氢键供体之外，还在空间上阻止(i-3)-羰基-(i + l)-酰胺主链氢键的形成。在此，基于对光合反应中心和细菌视紫红质中脯氨酸扭结螺旋的分析，以及对NBRF蛋白质序列数据库中鉴定出的含脯氨酸跨膜区段的分析结果，讨论了跨膜螺旋中脯氨酸扭结的一些结构方面。
