Schumacher Jörg, Joly Nicolas, Claeys-Bouuaert Inaki Leoz, Aziz Shaniza Abdul, Rappas Mathieu, Zhang Xiaodong, Buck Martin
Division of Biology, Imperial College London, London SW7 2AZ, UK.
J Mol Biol. 2008 Aug 1;381(1):1-12. doi: 10.1016/j.jmb.2008.05.075. Epub 2008 Jun 5.
AAA(+) proteins are ubiquitous mechanochemical ATPases that use energy from ATP hydrolysis to remodel their versatile substrates. The AAA(+) characteristic hexameric ring assemblies raise important questions about if and how six often identical subunits coordinate hydrolysis and associated motions. The PspF AAA(+) domain, PspF(1-275), remodels the bacterial sigma(54)-RNA polymerase to activate transcription. Analysis of ATP substrate inhibition kinetics on ATP hydrolysis in hexameric PspF(1-275) indicates negative homotropic effects between subunits. Functional determinants required for allosteric control identify: (i) an important link between the ATP bound ribose moiety and the SensorII motif that would allow nucleotide-dependent *-helical */beta subdomain dynamics; and (ii) establishes a novel regulatory role for the SensorII helix in PspF, which may apply to other AAA(+) proteins. Consistent with functional data, homotropic control appears to depend on nucleotide state-dependent subdomain angles imposing dynamic symmetry constraints in the AAA(+) ring. Homotropic coordination is functionally important to remodel the sigma(54) promoter. We propose a structural symmetry-based model for homotropic control in the AAA(+) characteristic ring architecture.
AAA(+)蛋白是普遍存在的机械化学ATP酶，它们利用ATP水解产生的能量来重塑其多样的底物。AAA(+)特征性的六聚体环组装引发了关于六个通常相同的亚基是否以及如何协调水解及相关运动的重要问题。PspF AAA(+)结构域，即PspF(1 - 275)，重塑细菌σ(54)-RNA聚合酶以激活转录。对六聚体PspF(1 - 275)中ATP水解的ATP底物抑制动力学分析表明亚基之间存在负协同效应。变构控制所需的功能决定因素确定：(i)ATP结合的核糖部分与SensorII基序之间的重要联系，这将允许核苷酸依赖性的α-螺旋/β亚结构域动态变化；以及(ii)确立了PspF中SensorII螺旋的新调节作用，这可能适用于其他AAA(+)蛋白。与功能数据一致，同促控制似乎取决于核苷酸状态依赖性的亚结构域角度，在AAA(+)环中施加动态对称约束。同促协调对于重塑σ(54)启动子在功能上很重要。我们提出了一个基于结构对称的AAA(+)特征性环结构中同促控制模型。
