MD simulations of anthrax edema factor: calmodulin complexes with mutations in the edema factor "switch a" region and docking of 3'-deoxy ATP into the adenylyl cyclase active site of wild-type and mutant edema factor variants.
MD simulations of anthrax edema factor: calmodulin complexes with mutations in the edema factor "switch a" region and docking of 3'-deoxy ATP into the adenylyl cyclase active site of wild-type and mutant edema factor variants.
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炭疽水肿因子的 MD 模拟：在水肿因子“开关 a”区域中具有突变的钙调蛋白复合物，并将 3-脱氧 ATP 对接至野生型和突变型水肿因子变体的腺苷酸环化酶活性位点。
DOI：
10.1080/07391102.2003.10506914
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发表时间：
2003
影响因子：
4.4
通讯作者：
Nelson,DonaldJ
中科院分区：
文献类型：
--
作者：
Zhao,Jingyan;Roy,StephanieA;Nelson,DonaldJ
炭疽杆菌是一种孢子形成的感染性细菌，它产生一种外毒素，称为水肿因子（EF），其部分功能是通过破坏内部信号通路。当与人类宿主细胞钙调素（CaM）复合时，EF成为一种活性腺苷酸环化酶，以不受控制的方式产生内部信号物质环AMP。最近，在存在和不存在底物类似物（3′-deoxy-ATP）的情况下，未复合的EF和EF：CaM复合物的晶体结构被报道。EF突变研究已经暗示了许多在CaM结合和/或腺苷酸环化酶活性位点的产生中重要的残基，所述腺苷酸环化酶活性位点由EF开关A、B和C区域在CaM结合后的移动形成。在这里，我们报告的两个EF：钙调素复合物，一个包含野生型EF和其他包含EF中的开关A区（L523，K525，Q526和V529）的残基簇已突变为丙氨酸的分子动力学（MD）模拟的结果。开关A突变导致开关C区的灵活性大幅增加，许多EF-CaM相互作用的破裂，CaM的羧基末端结构域的扩展，以及与EF复合的CaM的Ca 2+离子结合能力的变化。结果表明突变的开关A残基在维持紧凑的EF：CaM复合物中的重要性，该复合物似乎是产生全功能腺苷酸环化酶活性位点的先决条件。研究了突变EF活性位点区域的关键残基（K346、K353、H577、E588、D590和N639）对EF结合3′-脱氧-ATP底物类似物能力的影响。发现在位置583（N583 A）和577（H577 A）处的活性位点残基取代对于腺嘌呤环部分放置到配体-蛋白质复合物的X射线晶体结构中发现的位置中特别具有干扰性。
Bacillus anthracis, a spore-forming infectious bacterium, produces an exotoxin, called the edema factor (EF), that functions in part by disrupting internal signalling pathways. When complexed with human host cell calmodulin (CaM), EF becomes an active adenylyl cyclase, producing the internal signal substance cyclic-AMP in an uncontrolled fashion. Recently, the crystal structures for uncomplexed EF and EF:CaM complexes in the presence and absence of a substrate analog (3′-deoxy-ATP), were reported. EF mutational studies have implicated a number of residues important in CaM binding and/or in the generation of the adenylyl cyclase active site, formed by the movements of the EF switch A, B and C regions upon CaM binding. Here we report on the results of molecular dynamics (MD) simulations on two EF:CaM complexes, one containing wild-type EF and the other containing EF in which a cluster of residues in the switch A region (L523, K525, Q526 and V529) have been mutated to alanine. The switch A mutations cause a large increase in the flexibility of the switch C region, the rupture of a number of EF-CaM interactions, an expansion of the car-boxyl-terminal domain of CaM, and a change in the Ca2+ion binding abilities of the CaM that is in complex with EF. The results indicate the importance of the mutated switch A residues in maintaining a compact EF:CaM complex that appears to be a prerequisite for the generation of a fully-functional adenylyl cyclase active site. The effects of mutating key residues (K346, K353, H577, E588, D590 and N639) in the active site region of EF (to alanine) on the ability of EF to bind the 3′-deoxy-ATP substrate analog were also examined. Active-site residue substitutions at positions 583 (N583A) and 577 (H577A) were found to be particularly distruptive for the placement of the adenine ring moiety into the position found in the x-ray crystal structure of the ligand-protein complex.