Orengo C A, Thornton J M
Department of Biochemistry and Molecular Biology, University College, London, UK.
Structure. 1993 Oct 15;1(2):105-20. doi: 10.1016/0969-2126(93)90026-d.
By performing extensive pairwise structural comparisons, we recently identified a set of unique folds from the Brookhaven protein structure data bank. This analysis revealed considerable similarities between a large subgroup of the alpha+beta folds, which led us to re-examine the types of folds occurring in this class and the nature of the relationships between them.
Two major alpha+beta fold groups can be distinguished. In the first, described as alpha-beta sandwiches because alpha-helices and beta-strands occupy separate and distinct layers, a split beta alpha beta motif recurs frequently. The other group, alpha-beta rolls, contains fewer helices and is more diverse. In these, the beta-sheet has folded or rolled over, providing a cradle for the alpha-helix. A beta beta beta alpha-meander motif is found throughout the alpha+beta class.
Although many alpha-beta sandwiches have very similar folds, few share common functions and the active sites are distributed over the whole surface of the fold. The ability of the alpha-beta sandwich to accommodate a range of functions suggests that it is a stable fold and one that is able to adapt a number of sites to satisfy different functional requirements. In contrast, amongst the alpha-beta rolls, folds having the same roll type often have common functions.
通过进行广泛的成对结构比较，我们最近从布鲁克海文蛋白质结构数据库中识别出一组独特的折叠结构。该分析揭示了α+β折叠的一个大亚组之间存在相当大的相似性，这促使我们重新审视该类别中出现的折叠类型以及它们之间关系的本质。
可以区分出两个主要的α+β折叠组。在第一个组中，由于α螺旋和β链占据单独且不同的层，被描述为α-β三明治结构，一种分裂的βαβ基序频繁出现。另一组，即α-β卷，包含较少的螺旋且更加多样。在这些结构中，β折叠片层已经折叠或卷曲，为α螺旋提供了一个摇篮。在整个α+β类别中都发现了βββα曲折基序。
尽管许多α-β三明治结构具有非常相似的折叠，但很少有共同的功能，并且活性位点分布在折叠的整个表面。α-β三明治结构容纳一系列功能的能力表明它是一种稳定的折叠，并且能够适应多个位点以满足不同的功能需求。相比之下，在α-β卷中，具有相同卷曲类型的折叠通常具有共同的功能。
