Department Chemie, Technische Universität München, Lichtenbergstraße 4, D-85748, Garching, Germany.
Soft Matter Research Center and Department of Chemistry, Zhejiang University, 310027, P.R. China.
Sci Rep. 2017 Mar 14;7:43996. doi: 10.1038/srep43996.
Heat shock protein 90 (Hsp90) is an abundant molecular chaperone, involved in the folding and activation of 60% of the human kinome. The oncogenic tyrosine kinase v-Src is one of the most stringent client proteins of Hsp90, whereas its almost identical homolog c-Src is only weakly affected by the chaperone. Here, we perform atomistic molecular simulations and in vitro kinase assays to explore the mechanistic differences in the activation of v-Src and c-Src. While activation in c-Src is strictly controlled by ATP-binding and phosphorylation, we find that activating conformational transitions are spontaneously sampled in Hsp90-dependent Src mutants. Phosphorylation results in an enrichment of the active conformation and in an increased affinity for Hsp90. Thus, the conformational landscape of the mutated kinase is reshaped by a broken "control switch", resulting in perturbations of long-range electrostatics, higher activity and increased Hsp90-dependence.
热休克蛋白 90（Hsp90）是一种丰富的分子伴侣，参与了人类激酶组中 60%的蛋白质折叠和激活。致癌酪氨酸激酶 v-Src 是 Hsp90 的最严格的客户蛋白之一，而其几乎相同的同源物 c-Src 仅受到伴侣蛋白的轻微影响。在这里，我们进行了原子分子模拟和体外激酶测定，以探索 v-Src 和 c-Src 激活的机制差异。虽然 c-Src 的激活严格受 ATP 结合和磷酸化控制，但我们发现 Hsp90 依赖性 Src 突变体中自发地采样了激活构象转变。磷酸化导致活性构象的富集，并增加与 Hsp90 的亲和力。因此，突变激酶的构象景观被破坏的“控制开关”重塑，导致长程静电的干扰、更高的活性和对 Hsp90 的依赖性增加。
