A core region surrounded by a rim characterizes biological interfaces. We ascertain the importance of the core by showing the sequence entropies of the residues comprising the core to be smaller than those in the rim. Such a distinction is not seen in the 2-fold-related, nonphysiological interfaces formed in crystal lattices of monomeric proteins, thereby providing a procedure for characterizing the oligomeric state from crystal structures of protein molecules. This method is better than those that rely on the comparison of the sequence entropies in the interface and the rest of the protein surface, especially in cases where the surface harbors additional binding sites. To a good approximation there is a correlation between the accessible surface area lost because of complexation and ΔΔG values obtained through alanine-scanning mutagenesis (26-38 cal per Å2 of the surface buried) for residues located in the core, a relationship that is not discernable for rim residues. If, however, a residue participates in hydrogen bonding across the interface, the extent of stabilization is 52 cal/mol per 1 Å2 of the nonpolar surface area buried by the residue. As opposed to an amino acid classification used earlier, an environment-based grouping of residues yields a better discrimination in the sequence entropy between the core and the rim.
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机译:被边缘围绕的核心区域表征了生物界面。通过显示组成核心的残基的序列熵小于边缘中的序列熵,我们确定了核心的重要性。在单体蛋白质的晶格中形成的2倍相关非生理界面中看不到这种区别,从而提供了从蛋白质分子的晶体结构表征寡聚态的程序。该方法优于那些依靠比较界面和蛋白质表面其余部分的序列熵的方法,尤其是在表面具有其他结合位点的情况下。近似得出,由于络合而损失的可及表面积与通过丙氨酸扫描诱变(掩埋表面的Å 2 sup>为26-38 cal)获得的残留物之间的ΔΔG值之间存在相关性。核心,对于轮辋残留物无法辨别的关系。但是,如果残基参与界面上的氢键结合,则稳定程度为每1Å 2 sup>残基掩埋的非极性表面积的52 cal / mol。与先前使用的氨基酸分类相反,基于环境的残基分组可更好地区分核心和边缘之间的序列熵。
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