Sibanda B L, Thornton J M
Crystallography Department, Birkbeck College, London, England.
J Mol Biol. 1993 Jan 20;229(2):428-47. doi: 10.1006/jmbi.1993.1044.
A systematic study of homologous beta-hairpins in proteins of known structure reveals how insertions and deletions (herein known as indels) in the sequence are accommodated. The study was made for 12 protein families comprising 50 different structures, in which there were 49 independent hairpins. Each hairpin was classified according to its loop length and hydrogen bonding pattern. Most indels were found to occur in the loops and their frequency decreases rapidly with the size of the indel and approximately halves for each extra residue inserted. In very short loops, critical glycines are the primary determinants of loop structure and conversions between the two classic two-residue hairpin loops (with type I' and II' beta-turns) are quite common. Longer insertions are often accommodated by extending the beta-ladder and forming extra hydrogen bonds. There are also several indels that are not accommodated in the loop, but by forming a beta-bulge in one of the strands. This study should provide a useful aid to modelling hairpins in homologous structures.
一项对已知结构蛋白质中同源β-发夹的系统研究揭示了序列中的插入和缺失（在此称为插入缺失）是如何被容纳的。该研究针对12个蛋白质家族进行，这些家族包含50种不同结构，其中有49个独立的发夹。每个发夹根据其环长度和氢键模式进行分类。大多数插入缺失发生在环中，其频率随着插入缺失的大小而迅速降低，每插入一个额外的残基频率大约减半。在非常短的环中，关键的甘氨酸是环结构的主要决定因素，并且两种经典的两残基发夹环（具有I'型和II'型β-转角）之间的转换相当常见。较长的插入通常通过延伸β-折叠并形成额外的氢键来容纳。也有一些插入缺失不是在环中被容纳，而是通过在其中一条链中形成一个β-凸起。这项研究应该为同源结构中发夹的建模提供有用的帮助。
