Richardson J S, Getzoff E D, Richardson D C
Proc Natl Acad Sci U S A. 1978 Jun;75(6):2574-8. doi: 10.1073/pnas.75.6.2574.
A beta bulge is a region between two consecutive beta-type hydrogen bonds which includes two residues (positions 1 and 2) on one strand opposite a single residue (position x) on the other strand. Compared to regular beta structure, a beta bulge puts the usual alternation of side-chain direction out of register on one of the strands, introduces a slight bend in the beta sheet, and locally accentuates the usual right-handed strand twist. Almost all beta bulges are between antiparallel strands, usually between a narrow rather than a wide pair of hydrogen bonds. Ninety-one examples are listed. The two commonest types are the "classic" beta bulge, with position 1 in approximately alpha-helical conformation, and the "G1" beta bulge, with a required glycine at position 1 in approximately left-handed alpha-helical conformation, G1 bulges almost always occur in combination with a type II tight turn. The functional roles of beta bulges probably include compensating for the effects of a single-residue insertion or deletion within beta structure and providing the strong local twist required for form closed beta barrel structures.
β-凸起是两个连续的β型氢键之间的区域，其中一条链上有两个残基（位置1和2），与另一条链上的单个残基（位置x）相对。与规则的β结构相比，β-凸起使一条链上侧链方向的通常交替出现错位，在β折叠中引入轻微弯曲，并局部增强通常的右手链扭曲。几乎所有的β-凸起都在反平行链之间，通常在一对窄而非宽的氢键之间。列出了91个例子。最常见的两种类型是“经典”β-凸起，位置1处于近似α-螺旋构象，以及“G1”β-凸起，位置1需要一个甘氨酸处于近似左手α-螺旋构象，G1凸起几乎总是与II型紧密转角结合出现。β-凸起的功能作用可能包括补偿β结构内单个残基插入或缺失的影响，以及提供形成封闭β桶状结构所需的强烈局部扭曲。
