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arXiv 1208.1604q-bio.BMq-bio.PE
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协同进化位点对的推断:蛋白质3D结构中接触残基对的一个很好的预测器

Inference of Co-Evolving Site Pairs: an Excellent Predictor of Contact Residue Pairs in Protein 3D structures

Sanzo Miyazawa

摘要:

残基-残基相互作用将蛋白质折叠成独特的三维结构并使其发挥特定的功能,对每个残基位点施加结构和功能限制。对残基位点的选择性限制以氨基酸顺序记录在同源序列中,也记录在氨基酸取代的进化轨迹中。一个挑战是通过去除通过蛋白质内的其他残基或甚至通过其他分子的间接依赖性来提取残基位点之间的直接依赖性。最近尝试解开直接从间接依赖性的氨基酸类型之间的残基位置在多个序列比对揭示了推断的残基对耦合的强度是一个很好的预测残基-残基接近折叠结构。在这里,我们报告了一个替代的尝试推断共同发展的网站对并发和补偿性的替换网站之间的每个分支的系统发育树。首先,通过在机械密码子替换模型中最大化树的可能性来优化由相邻连接方法推断的系统发育树的分支长度以及其他参数。数量的平均变化,这是并发和补偿性替换的特点,伴随着替换在每个站点在每个分支的树估计每个替换的可能性。偏相关系数的特征变化沿分支站点之间的计算和用于排名共同发展的网站对。基于本共同进化评分的接触预测的准确性与从Pfam发布26.0中获得的15个蛋白质家族的蛋白质序列的最大熵模型所实现的准确性相当。此外,这种优异的准确性表明补偿性取代在蛋白质进化中具有重要意义。

英文摘要:

Residue-residue interactions that fold a protein into a unique three-dimensional structure and make it play a specific function impose structural and functional constraints on each residue site. Selective constraints on residue sites are recorded in amino acid orders in homologous sequences and also in the evolutionary trace of amino acid substitutions. A challenge is to extract direct dependences between residue sites by removing indirect dependences through other residues within a protein or even through other molecules. Recent attempts of disentangling direct from indirect dependences of amino acid types between residue positions in multiple sequence alignments have revealed that the strength of inferred residue pair couplings is an excellent predictor of residue-residue proximity in folded structures. Here, we report an alternative attempt of inferring co-evolving site pairs from concurrent and compensatory substitutions between sites in each branch of a phylogenetic tree. First, branch lengths of a phylogenetic tree inferred by the neighbor-joining method are optimized as well as other parameters by maximizing a likelihood of the tree in a mechanistic codon substitution model. Mean changes of quantities, which are characteristic of concurrent and compensatory substitutions, accompanied by substitutions at each site in each branch of the tree are estimated with the likelihood of each substitution. Partial correlation coefficients of the characteristic changes along branches between sites are calculated and used to rank co-evolving site pairs. Accuracy of contact prediction based on the present co-evolution score is comparable to that achieved by a maximum entropy model of protein sequences for 15 protein families taken from the Pfam release 26.0. Besides, this excellent accuracy indicates that compensatory substitutions are significant in protein evolution.

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