Formation of the myosin.ADP.gallium fluoride complex and its solution structure by small-angle synchrotron X-ray scattering.
Formation of the myosin.ADP.gallium fluoride complex and its solution structure by small-angle synchrotron X-ray scattering.
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通过小角同步加速器 X 射线散射观察肌球蛋白.ADP.氟化镓复合物的形成及其溶液结构。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
K. Wakabayashi
中科院分区：
文献类型：
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作者：
S. Maruta;Y. Uyehara;K. Homma;Y. Sugimoto;K. Wakabayashi
在MgADP存在下，氟化镓（GaFn）的一种新型磷酸盐类似物与肌球蛋白亚片段-1（S-1）形成三元复合物，与先前报道的氟化铝（AlF 4-）、氟化铍（BeFn）、氟化钪（ScFn）和钒酸盐（Vi）形成三元复合物的方式相同，这种复合物的形成可能模拟了ATP酶动力学途径中沿着的不同状态。这种新的复合物已被表征，并与其他复合物进行比较，以确定它是否形成肌球蛋白ATP酶的过渡态类似物。复合物形成迅速，但比BeFn复合物慢几倍。肌球蛋白、ADP、GaFn复合物在4 ℃时的半衰期约为50小时。肌球蛋白·ADP·GaFn复合物的形成伴随着色氨酸荧光的增加，与加入ATP时观察到的类似，但略低于M**·ADP·Pi复合物。当将GaFn加入到acto-myosin.ADP中时，acto-myosin不解离，S-1.ADP. GaFn复合物几乎不被肌动蛋白分解，类似于AlF_4-和ScFn复合物，但不同于BeFn和Vi复合物。用荧光标记和化学修饰的方法研究了与ATP结合最容易的SH_1、SH_2和RLR的定域构象，结果表明这些构象与M ~（**）·ADP·Pi态的构象非常相似。小角X-射线溶液散射表明，当S-1形成S-1.ADP. GaFn复合物时，回转半径值减小约3 A，表明复合物的形状变得紧凑或圆形，类似于ATP或与其他磷酸盐类似物的复合物存在时的形状，从而接近地模拟肌球蛋白 **.ADP.Pi状态。总体结果可能表明，复合物模拟的瞬态与其他复合物略有不同，但具有相似的整体构象沿着ATP酶动力学途径。
In the presence of MgADP, a novel phosphate analogue of gallium fluoride (GaFn) forms a ternary complex with the myosin subfragment-1 (S-1), in the same way that has been previously reported with aluminum fluoride (AlF4-), beryllium fluoride (BeFn), scandium fluoride (ScFn), and vanadate (Vi), and this complex formation may mimic different states along the ATPase kinetic pathway. This novel complex has been characterized and compared with other complexes to ascertain whether it forms a transition-state analogue of myosin ATPase. The complex formed quickly, although several times slower than the BeFn complex. The half-life of the myosin.ADP.GaFn complex was about 50 h at 4 degreesC. The formation of the myosin.ADP.GaFn complex was accompanied by an increase in tryptophane fluorescence, similar to that observed upon the addition of ATP, but slightly lower than that of the M**.ADP.Pi complex. Upon addition of GaFn to acto-myosin.ADP, acto-myosin did not dissociate, and the S-1.ADP.GaFn complex was scarcely decomposed by actin, like the AlF4- and ScFn complexes but unlike the BeFn and Vi complexes. The conformations at the localized region of SH1, SH2, and RLR, which are very accessible to the binding of ATP, were studied by fluorescent labeling and chemical modification, and the results suggested that these conformations are very similar to that of the M**.ADP.Pi state. Small-angle X-ray solution scattering showed that the radius of gyration value decreases by about 3 A when S-1 forms an S-1.ADP.GaFn complex, suggesting that the shape of the complex becomes compact or rounded in shape, similar to that in the presence of ATP or complexes with other phosphate analogues, and thus mimics the myosin**.ADP.Pi state closely. The overall results may indicate that the complex mimics a somewhat different transient state from that of other complexes but has a similar global conformation along the ATPase kinetic pathway.