Four-α-helix bundle with designed anesthetic binding pockets.: Part II:: Halothane effects on structure and dynamics
Four-α-helix bundle with designed anesthetic binding pockets.: Part II:: Halothane effects on structure and dynamics
复制标题
DOI：
10.1529/biophysj.107.117853
复制
发表时间：
2008-06-01
影响因子：
3.4
通讯作者：
Tang, Pei
中科院分区：
文献类型：
--
作者：
Cui, Tanxing;Bondarenko, Vasyl;Tang, Pei
作为挥发性麻醉剂蛋白靶点的模型，二聚体4 -a-螺旋束（a α (2)-L1M/L38M）(2)被设计成包含一个长疏水核心，由四个两亲a-螺旋包围，用于特异性麻醉剂结合。（A α (2)-L1M/L38M）(2)在没有麻醉剂的情况下的结构和动力学分析（另一项研究）表明，（A α (2)-L1M/L38M）(2)是一个高度动态的反平行二聚体，具有四个螺旋的不对称排列和从水相到疏水核心的横向通路。在这项研究中，我们确定了（A α 2- l1m /L38M）(2)在氟烷（一种临床使用的挥发性麻醉剂）存在下的高分辨率核磁共振结构。高溶液核磁共振结构（主根均方差为1.72埃（2JST））和核磁共振结合测量表明，伯代氟烷结合位点位于每个单体的W15的两个侧链之间，与最初设计的麻醉剂结合位点不同。与残基A44和L18的疏水相互作用也有助于稳定结合的氟烷。而氟烷在单体结构上产生微小的变化，二聚体的四元排列被移动了大约半螺旋旋转和相互扭曲，这导致通向疏水核心的侧向通路关闭。定量动力学分析，包括弛豫数据的Modelfree分析和carr - pur细胞- meiboom - Gill横向弛豫色散测量，表明最深刻的麻醉效应是抑制结合位点附近和远处的构象交换。我们的研究结果揭示了一种新的机制，在麻醉分子和它的蛋白质靶标之间诱导配合，与蛋白质动力学变化的直接后果是在全局而不是局部范围内发生变化。这一机制可能是麻醉作用于神经元蛋白的普遍机制。
As a model of the protein targets for volatile anesthetics, the dimeric four-a-helix bundle, (A alpha(2)-L1M/L38M)(2), was designed to contain a long hydrophobic core, enclosed by four amphipathic a-helices, for specific anesthetic binding. The structural and dynamical analyses of (A alpha(2)-L1M/L38M)(2) in the absence of anesthetics (another study) showed a highly dynamic antiparallel dimer with an asymmetric arrangement of the four helices and a lateral accessing pathway from the aqueous phase to the hydrophobic core. In this study, we determined the high-resolution NMR structure of (A alpha 2-L1M/L38M)(2) in the presence of halothane, a clinically used volatile anesthetic. The high-solution NMR structure, with a backbone root mean-square deviation of 1.72 angstrom(2JST), and the NMR binding measurements revealed that the primary halothane binding site is located between two side-chains of W15 from each monomer, different from the initially designed anesthetic binding sites. Hydrophobic interactions with residues A44 and L18 also contribute to stabilizing the bound halothane. Whereas halothane produces minor changes in the monomer structure, the quaternary arrangement of the dimer is shifted by about half a helical turn and twists relative to each other, which leads to the closure of the lateral access pathway to the hydrophobic core. Quantitative dynamics analyses, including Modelfree analysis of the relaxation data and the Carr-Purcell-Meiboom- Gill transverse relaxation dispersion measurements, suggest that the most profound anesthetic effect is the suppression of the conformational exchange both near and remote from the binding site. Our results revealed a novel mechanism of an induced fit between anesthetic molecule and its protein target, with the direct consequence of protein dynamics changing on a global rather than a local scale. This mechanism may be universal to anesthetic action on neuronal proteins.