Centre de Recherches de Biochimie Macromoléculaire, CNRS UMR-5237, University of Montpellier 1 and 2, France.
FEBS J. 2010 Jun;277(12):2673-82. doi: 10.1111/j.1742-464X.2010.07684.x.
We analysed the structural properties of protein regions containing arrays of perfect and nearly perfect tandem repeats. Naturally occurring proteins with perfect repeats are practically absent among the proteins with known 3D structures. The great majority of such regions in the Protein Data Bank are found in the proteins designed de novo. The abundance of natural structured proteins with tandem repeats is inversely correlated with the repeat perfection: the chance of finding natural structured proteins in the Protein Data Bank increases with a decrease in the level of repeat perfection. Prediction of intrinsic disorder within the tandem repeats in the SwissProt proteins supports the conclusion that the level of repeat perfection correlates with their tendency to be unstructured. This correlation is valid across the various species and subcellular localizations, although the level of disordered tandem repeats varies significantly between these datasets. On average, in prokaryotes, tandem repeats of cytoplasmic proteins were predicted to be the most structured, whereas in eukaryotes, the most structured portion of the repeats was found in the membrane proteins. Our study supports the hypothesis that, in general, the repeat perfection is a sign of recent evolutionary events rather than of exceptional structural and (or) functional importance of the repeat residues.
我们分析了含有完美和近乎完美串联重复序列的蛋白质区域的结构特性。在具有已知 3D 结构的蛋白质中，实际上不存在天然存在的具有完美重复的蛋白质。蛋白质数据库中此类区域的绝大多数存在于从头设计的蛋白质中。具有串联重复的天然结构蛋白质的丰度与重复的完美程度呈负相关：在蛋白质数据库中发现天然结构蛋白质的机会随着重复完美程度的降低而增加。在 SwissProt 蛋白质中对串联重复的固有无序性的预测支持这样的结论，即重复的完美程度与其无规则结构的趋势相关。尽管这些数据集之间的无序串联重复的水平差异很大，但这种相关性在各种物种和亚细胞定位中都是有效的。平均而言，在原核生物中，预测细胞质蛋白质的串联重复序列最具结构特征，而在真核生物中，重复序列的最具结构部分位于膜蛋白中。我们的研究支持这样的假设，即在一般情况下，重复的完美程度是最近进化事件的标志，而不是重复残基的特殊结构和（或）功能重要性的标志。
