X-ray structures of the MgADP, MgATP gamma S, and MgAMPPNP complexes of the Dichyostelium discoideum myosin motor domain
X-ray structures of the MgADP, MgATP gamma S, and MgAMPPNP complexes of the Dichyostelium discoideum myosin motor domain
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DOI：
10.1021/bi9712596
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发表时间：
1997-09-30
期刊：
影响因子：
2.9
通讯作者：
Rayment, I
中科院分区：
文献类型：
--
作者：
Gulick, AM;Bauer, CB;Rayment, I
报道了盘基网柄菌肌球蛋白II(S1dC)与镁AMPPNP、镁ATP、S和镁ADP络合物的三维结构，其分辨率分别为2.1、1.9和2.1。晶体是通过共结晶获得的，与S1dC的晶体是同构的。镁ADP。访问数/每百万人：Reach for[Fisher，A.J.(1995)生物化学34,8960-8972]。在这三种结构中，都可以清楚地看到整个核苷酸的电子密度，所有三种络合物的总体结构都与氟化铍络合物非常相似，这表明ATPGamma/S和AMPPNP的生理效应的不同是由于AMPPNP对肌球蛋白的亲和力较低而导致肌球蛋白肌动蛋白结合状态和去肌动蛋白状态平衡的改变。在S1DC中。MgAMPPNP，桥联氮的存在促使ASN(233)的侧链旋转，从而破坏核苷酸结合口袋中的氢键模式，并改变核糖羟基周围的水结构。这一变化似乎是AMPPNP与肌球蛋白相对、与ATPGamma S亲和力降低的原因。与G蛋白不同，S1dC中与核苷酸配位的配体的构象没有重大变化。镁ADP。这是由于三个水分子采用了三个氧在γ-磷酸上的大致位置，并保持了与镁离子和蛋白质分子的相互作用。有趣的是，硫代磷酸基团在S1DC中很明显。镁-三磷酸腺苷-伽马-S，尽管它被肌球蛋白缓慢地水解。这表明在这里和在鸡骨骼肌球蛋白亚片段-L中观察到的构象[Rayment，I.，ct.(1993)Science 261，50-58]不能水解三磷酸腺苷，并代表肌球蛋白预水解弱结合状态的结构。
The three-dimensional structures of the truncated myosin head from Dictyostelium discoideum myosin II (S1dC) complexed with MgAMPPNP, MgATP gamma S, and MgADP are reported at 2.1, 1.9, and 2.1 Angstrom 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 ATP gamma/S 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 Asn(233) 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 ATP gamma S. 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 . MgATP gamma S even though it is slowly hydrolyzed by myosin. This suggests that the conformation observed here and in chicken skeletal myosin subfragment-l [Rayment, I., ct al. (1993) Science 261, 50-58] is unable to hydrolyze ATP and represents the structure of the prehydrolysis weak binding state of myosin.