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arXiv 1905.04493q-bio.BM
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重复序列蛋白质序列空间的大小和结构

Size and structure of the sequence space of repeat proteins

Jacopo Marchi, Ezequiel A. Galpern, Rocio Espada, Diego U. Ferreiro, Aleksandra M. Walczak, Thierry Mora

摘要:

蛋白质序列的编码空间是由功能和稳定性要求所设定的进化约束所形成的。我们表明,一个给定的蛋白质家族的编码空间-该家族中的序列总数-可以估计使用模型的最大熵训练的多个序列比对的天然存在的氨基酸序列。我们分析和计算了三个丰富重复蛋白家族的大小,这些家族的成员是由~ 30个氨基酸的保守部分的许多重复组成的大蛋白。虽然在比对的每个位置处的氨基酸保守性解释了相对于完全随机序列的多样性的大部分减少,但是我们发现在不同位置处的氨基酸使用之间的相关性显著地影响多样性。我们量化了不同类型的相关性,功能和进化,对序列多样性的影响。对家族编码空间的详细结构的分析揭示了一个崎岖的景观,具有许多具有层次结构的不同大小的局部能量极小值,让人想起物理学中自旋玻璃的fustrated能量景观。这种聚集的结构表明每个家族内亚型的多样性,并提出了蛋白质设计的新策略。

英文摘要:

The coding space of protein sequences is shaped by evolutionary constraints set by requirements of function and stability. We show that the coding space of a given protein family--the total number of sequences in that family--can be estimated using models of maximum entropy trained on multiple sequence alignments of naturally occuring amino acid sequences. We analyzed and calculated the size of three abundant repeat proteins families, whose members are large proteins made of many repetitions of conserved portions of ~ 30 amino acids. While amino acid conservation at each position of the alignment explains most of the reduction of diversity relative to completely random sequences, we found that correlations between amino acid usage at different positions significantly impact that diversity. We quantified the impact of different types of correlations, functional and evolutionary, on sequence diversity. Analysis of the detailed structure of the coding space of the families revealed a rugged landscape, with many local energy minima of varying sizes with a hierarchical structure, reminiscent of fustrated energy landscapes of spin glass in physics. This clustered structure indicates a multiplicity of subtypes within each family, and suggests new strategies for protein design.

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