X-ray structure of the magnesium(II)-pyrophosphate complex of the truncated head of Dictyostelium discoideum myosin to 2.7 A resolution.
X-ray structure of the magnesium(II)-pyrophosphate complex of the truncated head of Dictyostelium discoideum myosin to 2.7 A resolution.
复制标题
盘基网柄菌肌球蛋白截头的镁 (II)-焦磷酸复合物的 X 射线结构，分辨率为 2.7 A。
DOI：
10.1021/bi00028a005
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发表时间：
1995
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：
Smith,CA;Rayment,I
摘要：用2.7 A分辨率的分子置换法测定了Dictyostelium myosin截断头的焦磷酸镁配合物的结构，并将其细化到晶体学r因子为16.0%。晶体属于正交空间群P2{2\2，其中a= 105.2 a, b= 182.1 a, c=54.5 a。焦磷酸镁周围的蛋白质构象与adp -氟化铍镁在活性位点结合时的构象非常相似。后一种复合物在水解前模拟ATP的结合。焦磷酸盐分子占据了/？和y-磷酸位点，其中两个磷原子与/3-磷酸和氟化铍捕获的ADP的BeF*部分处于相同的位置。在两种结构中，周围的活性位点残基几乎完全重叠，PPi与蛋白质的氢键相互作用基本上是相同的。MgPPi和MgADP* BeFx复合物与SlDc之间的相似性表明，当ATP与肌动蛋白结合并降低肌动蛋白对肌动蛋白的亲和力时发生的构象变化是由核苷酸的y和/3磷酸基团结合引起的。这意味着底物的剩余部分的作用是增加对肌凝蛋白的结合亲和力，从而推动肌凝蛋白与肌动蛋白分离的平衡。
Revised Manuscript Received May 9, 1995s abstract: The structure of the magnesium pyrophosphate complex of the truncated head of Dictyostelium myosin has beendetermined by molecular replacement at 2.7 A resolution and refined to a crystallographic R-factor of 16.0%. The crystals belong to the orthorhombic space group P2 {2\2, where a= 105.2 A, b= 182.1 A, and c=54.5 A. The conformation of the protein around the magnesium pyrophosphate is very similar to that seen when magnesium ADP—beryllium fluoride binds in the active site. The latter complex mimics the binding of ATP prior to hydrolysis. The pyrophosphate molecule occupiesthe/?-and y-phosphate sites, where the two phosphorus atoms are in the same positions as the/3-phosphate and the BeF* moiety of the beryllium fluoride-trapped ADP. The surrounding active site residues are almost perfectly superimposable in the two structures and the hydrogen-bonding interactions that the PPi makes with the protein are essentially identical. The similarity between the MgPPi and MgADP* BeFx complex with SlDc suggests that the conformational change, which occurs when ATP binds to actomyosin and which reduces the affinity of myosin for actin, is caused by the binding of the y-and/3-phosphate groups of the nucleotide. This then implies that the role of the remainder of the substrate is to increase the binding affinity for myosin and thus to drive the equilibrium toward dissociation of myosin from actin.