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首页> 外文期刊>Biochemistry >X-ray structures of the MgADP, MgATPgammaS, and MgAMPPNP complexes of the Dictyostelium discoideum myosin motor domain
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X-ray structures of the MgADP, MgATPgammaS, and MgAMPPNP complexes of the Dictyostelium discoideum myosin motor domain

机译：盘基网柄菌肌球蛋白运动域的MgADP，MgATPgammaS和MgAMPPNP配合物的X射线结构

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摘要

The three-dimensional structures of the truncated myosin head from Dictyostelium discoideum myosin II (S1dC) complexed with MgAMPPNP, MgATPgammaS, and MgADP are reported at 2.1, 1.9, and 2.1 A resolution, respectively. Crystals were obtained by cocrystallization and were isomorphous with respect to those of S1dC. MgADP.BeFx [Fisher, A. J., et al. (1995) Biochemistry 34, 8960-8972]. In all three structures, the electron density for the entire nucleotide was clearly discernible. The overall structures of all three complexes are very similar to that of the beryllium fluoride complex which suggests that the differences in the physiological effects of ATPgammaS and AMPPNP are due to the changes in the equilibrium between the actin-bound and actin-free states of myosin caused by the lower affinity of AMPPNP for myosin. In S1dC.MgAMPPNP, the presence of the bridging nitrogen prompts the side chain of Asn233 to rotate which disrupts the hydrogen bonding pattern in the nucleotide binding pocket and alters the water structure surrounding the ribose hydroxyl groups. It appears that this change is responsible for the reduced affinity of AMPPNP for myosin relative to ATPgammaS. In contrast to the G-proteins, there is no major change in the conformation of the ligands that coordinate the nucleotide in S1dC.MgADP. This is due to three water molecules that adopt the approximate positions of the three oxygens on the gamma-phosphate and maintain the interactions with the Mg2+ ion and protein molecule. Interestingly, the thiophosphate group is evident in S1dC.MgATPgammaS even though it is slowly hydrolyzed by myosin. This suggests that the conformation observed here and in chicken skeletal myosin subfragment-1 [Rayment, I., et al. (1993) Science 261, 50-58] is unable to hydrolyze ATP and represents the structure of the prehydrolysis weak binding state of myosin.
机译：分别报道了与MgAMPPNP，MgATPgammaS和MgADP复合的盘基网柄菌肌球蛋白II（S1dC）的截短的肌球蛋白头的三维结构，分辨率分别为2.1、1.9和2.1A。通过共结晶获得晶体，并且相对于S1dC晶体是同构的。 MgADP.BeFx [Fisher，A.J。，等。 （1995）Biochemistry 34，8960-8972]。在所有三个结构中，整个核苷酸的电子密度是清晰可辨的。这三种复合物的整体结构与氟化铍复合物的结构非常相似，这表明ATPgammaS和AMPPNP的生理效应差异是由于肌球蛋白的肌动蛋白结合状态与无肌动蛋白状态之间平衡的变化引起的。是由于AMPPNP对肌球蛋白的亲和力较低。在S1dC.MgAMPPNP中，桥连氮的存在促使Asn233的侧链旋转，这破坏了核苷酸结合袋中的氢键结合模式，并改变了核糖羟基周围的水结构。看来，这种变化是AMPPNP对肌球蛋白相对于ATPgammaS亲和力降低的原因。与G蛋白相反，与S1dC.MgADP中的核苷酸配位的配体构象没有重大变化。这是由于三个水分子采用了三个氧在γ-磷酸盐上的近似位置，并保持了与Mg2 +离子和蛋白质分子的相互作用。有趣的是，硫代磷酸酯基团在S1dC.MgATPgammaS中很明显，即使它被肌球蛋白缓慢水解。这表明在这里和在鸡骨骼肌肌球蛋白亚片段1中观察到的构象[Rayment，I。，等人。 （1993）Science 261，50-58]不能水解ATP并且代表肌球蛋白的预水解弱结合状态的结构。

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