Most signal transduction pathways in humans are regulated by protein kinases through phosphorylation of their protein substrates. Typical eukaryotic protein kinases are of two major types: those that phosphorylate-specific sequences containing tyrosine (~90 kinases) and those that phosphorylate either serine or threonine (~395 kinases). The highly conserved catalytic domain of protein kinases comprises a smaller N lobe and a larger C lobe separated by a cleft region lined by the activation loop. Prior studies find that protein tyrosine kinases recognize peptide substrates by binding the polypeptide chain along the C-lobe on one side of the activation loop, while serine/threonine kinases bind their substrates in the cleft and on the side of the activation loop opposite to that of the tyrosine kinases. Substrate binding structural studies have been limited to four families of the tyrosine kinase group, and did not include Src tyrosine kinases. We examined peptide-substrate binding to Src using paramagnetic-relaxation-enhancement NMR combined with molecular dynamics simulations. The results suggest Src tyrosine kinase can bind substrate positioning residues C-terminal to the phosphoacceptor residue in an orientation similar to serine/threonine kinases, and unlike other tyrosine kinases. Mutagenesis corroborates this new perspective on tyrosine kinase substrate recognition. Rather than an evolutionary split between tyrosine and serine/threonine kinases, a change in substrate recognition may have occurred within the TK group of the human kinome. Protein tyrosine kinases have long been therapeutic targets, but many marketed drugs have deleterious off-target effects. More accurate knowledge of substrate interactions of tyrosine kinases has the potential for improving drug selectivity.

中文翻译：

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底物与 Src 的结合：从 NMR 和分子动力学对酪氨酸激酶底物识别的新视角。

人类中的大多数信号转导途径是由蛋白激酶通过其蛋白底物的磷酸化来调节的。典型的真核蛋白激酶有两种主要类型：一种是磷酸化含有酪氨酸的特异性序列（约 90 个激酶），另一种是磷酸化丝氨酸或苏氨酸（约 395 个激酶）。蛋白激酶的高度保守的催化结构域包括一个较小的 N 叶和一个较大的 C 叶，由一个由激活环排列的裂隙区域隔开。先前的研究发现，蛋白酪氨酸激酶通过沿着激活环一侧的 C 小叶结合多肽链来识别肽底物，而丝氨酸/苏氨酸激酶则在裂隙中和激活环相反的一侧结合其底物。的酪氨酸激酶。底物结合结构研究仅限于酪氨酸激酶组的四个家族，不包括 Src 酪氨酸激酶。我们使用顺磁弛豫增强核磁共振结合分子动力学模拟检查了肽底物与 Src 的结合。结果表明，Src 酪氨酸激酶可以将底物定位残基 C 端与磷酸受体残基结合，其方向与丝氨酸/苏氨酸激酶相似，但与其他酪氨酸激酶不同。诱变证实了酪氨酸激酶底物识别的这一新观点。而不是酪氨酸和丝氨酸/苏氨酸激酶之间的进化分裂，底物识别的变化可能发生在人类激酶组的 TK 组内。蛋白酪氨酸激酶长期以来一直是治疗靶点，但许多上市药物具有有害的脱靶效应。更准确地了解酪氨酸激酶的底物相互作用具有提高药物选择性的潜力。