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首页> 外文期刊>Journal of Molecular Biology >Tyrosine hydrogen bonds make a large contribution to protein stability
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Tyrosine hydrogen bonds make a large contribution to protein stability

机译：酪氨酸氢键对蛋白质稳定性有很大贡献

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The aim of this study was to gain a better understanding of the contribution of hydrogen bonds by tyrosine -OH groups to protein stability. The amino acid sequences of RNases Sa and Sa3 are 69% identical and each contains eight Tyr residues with seven at equivalent structural positions. We have measured the stability of the 16 tyrosine to phenylalanine mutants. For two equivalent mutants, the stability increases by 0.3 kcal/mol (RNase Sa Y30F) and 0.5 kcal/mol (RNase Sa3 Y33F) (1 kcal = 4.184 kJ). For all of the other mutants, the stability decreases with the greatest decrease being 3.6 kcal/mol for RNase Sa Y52F. Seven of the 16 tyrosine residues form intramolecular hydrogen bonds and the average decrease in stability for these is 2.0(+/-1.0) kcal/mol. For the nine tyrosine residues that do not form intramolecular hydrogen bonds, the, average decrease in stability is 0.4(+/-0.6) kcal/mol. Thus, most tyrosine -OH groups contribute favorably to protein stability even if they do not form intramolecular hydrogen bonds. Generally, the stability changes for equivalent positions in the two proteins are remarkably similar. Crystal structures were determined for two of the tyrosine to phenylalanine mutants of RNase Sa: Y80F (1.2 Angstrom), and Y86F (1.7 Angstrom). The structures are very similar to that of wild-type RNase Sa, and the hydrogen bonding partners of the tyrosine residues always form intermolecular hydrogen bonds to water in the mutants. These results provide further evidence that the hydrogen bonding and van der Waals interactions of polar groups in the tightly packed interior of folded proteins are more favorable than similar interactions with water in the unfolded protein, and that polar group burial makes a substantial contribution to protein stability.
机译：这项研究的目的是更好地了解酪氨酸-OH基团对氢键对蛋白质稳定性的贡献。 RNase Sa和Sa3的氨基酸序列具有69％的同一性，每个氨基酸序列包含八个Tyr残基，在相同的结构位置具有七个。我们已经测量了16个酪氨酸对苯丙氨酸突变体的稳定性。对于两个等效的突变体，稳定性提高了0.3 kcal / mol（RNase Sa Y30F）和0.5 kcal / mol（RNase Sa3 Y33F）（1 kcal = 4.184 kJ）。对于所有其他突变体，RNA酶Sa Y52F的稳定性降低，最大降低为3.6kcal / mol。 16个酪氨酸残基中有7个形成分子内氢键，其平均稳定性下降为2.0（+/- 1.0）kcal / mol。对于不形成分子内氢键的九个酪氨酸残基，稳定性的平均降低为0.4（+/- 0.6）kcal / mol。因此，即使大多数酪氨酸-OH基团不形成分子内氢键，它们也有利于蛋白质的稳定性。通常，两种蛋白质中等同位置的稳定性变化非常相似。确定了RNase Sa的两个酪氨酸至苯丙氨酸突变体的晶体结构：Y80F（1.2埃）和Y86F（1.7埃）。其结构与野生型RNase Sa的结构非常相似，酪氨酸残基的氢键伙伴在突变体中始终与水形成分子间氢键。这些结果提供了进一步的证据，表明紧密折叠的蛋白质内部极性基团的氢键键合和范德华相互作用比未折叠蛋白质中与水的相似相互作用更有利，并且极性基团的埋藏对蛋白质稳定性起了重要作用。 。

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