Chan A W, Hutchinson E G, Harris D, Thornton J M
Department of Biochemistry and Molecular Biology, University College, London, United Kingdom.
Protein Sci. 1993 Oct;2(10):1574-90. doi: 10.1002/pro.5560021004.
A beta-bulge is a region of irregularity in a beta-sheet involving two beta-strands. It usually involves two or more residues in the bulged strand opposite to a single residue on the adjacent strand. These irregularities in beta-sheets were identified and classified automatically, extending the definition of beta-bulges given by Richardson et al. (Richardson, J.S., Getzoff, E.D., & Richardson, D.C., 1978, Proc. Natl. Acad. Sci. USA 75, 2574-2578). A set of 182 protein chains (170 proteins) was used, and a total of 362 bulges were extracted. Five types of beta-bulges were found: classic, G1, wide, bent, and special. Their characteristic amino acid preferences were found for most classes of bulges. Basically, bulges occur frequently in proteins; on average there are more than two bulges per protein. In general, beta-bulges produce two main changes in the structure of a beta-sheet: (1) disrupt the normal alternation of side-chain direction; (2) accentuate the twist of the sheet, altering the direction of the surrounding strands.
β-凸起是β-折叠中涉及两条β-链的不规则区域。它通常在凸起链中涉及两个或更多残基，与相邻链上的单个残基相对。β-折叠中的这些不规则性已被自动识别和分类，扩展了Richardson等人给出的β-凸起的定义（Richardson, J.S., Getzoff, E.D., & Richardson, D.C., 1978, Proc. Natl. Acad. Sci. USA 75, 2574 - 2578）。使用了一组182条蛋白质链（170种蛋白质），共提取出362个凸起。发现了五种类型的β-凸起：经典型、G1型、宽型、弯曲型和特殊型。对于大多数类型的凸起，发现了它们特有的氨基酸偏好。基本上，凸起在蛋白质中频繁出现；平均每个蛋白质有两个以上的凸起。一般来说，β-凸起会在β-折叠结构中产生两个主要变化：（1）破坏侧链方向的正常交替；（2）加剧折叠的扭曲，改变周围链的方向。
