Efimov A V
Mol Biol (Mosk). 1982 Jul-Aug;16(4):799-806.
A structural unit common for all the known beta-proteins as well as for some others is considered in the paper. The simplest variant of this unit consists of four consecutive beta-strands denoted as a, b, c and d. Three of the strands, a, b and d, form an antiparallel beta-sheet, and the fourth, c, lies in the other layer of a layered protein sandwich structure. The strands, b and d, are parallel in the beta-sheet and together with the c-strand fold into a right-handed bcd-superhelix which is analogous to the superhelix formed by beta alpha beta regions. An a-strand is found between the strands b and d and antiparallel to them. Such locally ordered regions of proteins are described here as abcd-units. In all the known proteins the abcd-unit was found to be always at the edge of a protein bilayer. The remaining strands of a molecule or a domain are always located on the same side of the abcd-unit where the d-strand lies. It is shown that the packing of beta-strands in the beta-proteins depends on the packing of the other strands. The structural approach suggested here allows the packing of beta-strands in three-dimensions to be obtained if the abcd-unit is taken as the embryo of folding.
本文探讨了所有已知β-蛋白以及其他一些蛋白共有的一种结构单元。该单元最简单的变体由四条连续的β链组成，分别标记为a、b、c和d。其中三条链，a、b和d，形成一个反平行β折叠片层，第四条链c位于层状蛋白质夹心结构的另一层。在β折叠片中，b链和d链是平行的，它们与c链一起折叠成一个右手bcd超螺旋，类似于由β-α-β区域形成的超螺旋。在b链和d链之间发现一条a链，且与它们反平行。蛋白质中这种局部有序区域在此被描述为abcd单元。在所有已知蛋白质中，abcd单元总是位于蛋白质双层的边缘。分子或结构域的其余链总是位于abcd单元中d链所在的同一侧。结果表明，β-蛋白中β链的堆积取决于其他链的堆积。如果将abcd单元作为折叠的起始结构，这里提出的结构方法可以得到β链在三维空间中的堆积方式。
