Kintses Bálint, Gyimesi Máté, Pearson David S, Geeves Michael A, Zeng Wei, Bagshaw Clive R, Málnási-Csizmadia András
Department of Biochemistry, Eötvös Lorand University, Budapest, Hungary.
EMBO J. 2007 Jan 10;26(1):265-74. doi: 10.1038/sj.emboj.7601482.
The conserved switch 1 loop of P-loop NTPases is implicated as a central element that transmits information between the nucleotide-binding pocket and the binding site of the partner proteins. Recent structural studies have identified two states of switch 1 in G-proteins and myosin, but their role in the transduction mechanism has yet to be clarified. Single tryptophan residues were introduced into the switch 1 region of myosin II motor domain and studied by rapid reaction methods. We found that in the presence of MgADP, two states of switch 1 exist in dynamic equilibrium. Actin binding shifts the equilibrium towards one of the MgADP states, whereas ATP strongly favors the other. In the light of electron cryo-microscopic and X-ray crystallographic results, these findings lead to a specific structural model in which the equilibrium constant between the two states of switch 1 is coupled to the strength of the actin-myosin interaction. This has implications for the enzymatic mechanism of G-proteins and possibly P-loop NTPases in general.
P 环 NTP 酶保守的开关 1 环被认为是在核苷酸结合口袋与伙伴蛋白结合位点之间传递信息的核心元件。最近的结构研究已经确定了 G 蛋白和肌球蛋白中开关 1 的两种状态，但其在转导机制中的作用尚未阐明。将单个色氨酸残基引入肌球蛋白 II 运动结构域的开关 1 区域，并通过快速反应方法进行研究。我们发现，在 MgADP 存在的情况下，开关 1 的两种状态处于动态平衡。肌动蛋白结合使平衡向其中一种 MgADP 状态移动，而 ATP 则强烈倾向于另一种状态。根据电子冷冻显微镜和 X 射线晶体学结果，这些发现得出了一个特定的结构模型，其中开关 1 两种状态之间的平衡常数与肌动蛋白 - 肌球蛋白相互作用的强度相关联。这对 G 蛋白以及可能一般的 P 环 NTP 酶的酶促机制具有重要意义。
