Onishi Hirofumi, Ohki Takashi, Mozhizuki Naoki, Morales Manuel F
Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka 565-8565.
Adv Exp Med Biol. 2003;538:175-81; discussion 181. doi: 10.1007/978-1-4419-9029-7_16.
When ATP binds to the active site of myosin heads, Switch II undergoes a large conformational change and the cleft surrounding the bound gamma-phosphate closes. In the closed state, Glu470 in Switch II comes together with Arg247 in Switch I to form a salt-bridge. Here, the functional significance of the two bridging residues was tested by using site-directed mutagenesis. We conclude from such tests that (a) the attractive force between Arg247 and the gamma-phosphate of ATP moves the cleft to close, and (b) during hydrolysis, Glu470 is intimately involved in positioning the lytic water for the attack on the gamma-phosphorus. We also speculate on how the salt-bridge between Arg247 and Glu470 is related to hydrolysis.
当ATP结合到肌球蛋白头部的活性位点时，开关II会发生巨大的构象变化，围绕结合的γ-磷酸基团的裂缝会关闭。在关闭状态下，开关II中的Glu470与开关I中的Arg247结合形成盐桥。在此，通过定点诱变测试了这两个桥接残基的功能意义。我们从这些测试中得出结论：（a）Arg247与ATP的γ-磷酸基团之间的吸引力使裂缝关闭，并且（b）在水解过程中，Glu470密切参与定位裂解水以攻击γ-磷。我们还推测了Arg247和Glu470之间的盐桥与水解是如何相关的。
