Multiple Activity Patterns of Acetylcholine Receptors

描述（由申请人提供）：神经肌肉突触的信号需要C（闭通道）O（笔通道）乙酰胆碱受体（achr）的“门控”。这种变构转变的热力学基础很好理解：从神经末端释放的递质分子结合到对O比C具有更高亲和力的achr上，从而增加通道打开的可能性。CO内部的微观事件则不太确定。我们将使用单通道动力学和ph值分析来探测AChR门控的内部，并阐明该反应中的超快速蛋白质重排。到目前为止，结果表明，achr从c到o的变化需要4个步骤。第一个移动的氨基酸不是在传递体结合位点，而是在连接亚基的M2和M3螺旋的远处膜结构域连接体上。此外，M2（所有亚基）中的双门的解锁发生在最后2个门激活步骤中。大多数侧链门控运动是“重新安置”事件，只具有局部能量后果。我们将研究两个关于AChR门控的新假设：1)结合位点和门之间的通信不是通过结构力学过程，而是通过整个主干的振动熵；2)变构通信开始于激动剂与静息受体的低亲和力结合。

DESCRIPTION (provided by applicant): Signaling at the neuromuscular synapse requires C(losed-channel)O(pen-channel) 'gating' of acetylcholine receptors (AChRs). The thermodynamic foundation of this allosteric transition is well understood: transmitter molecules released from the nerve terminal bind to AChRs with higher affinity to O vs. C to increase the probability that the channel is Open. The microscopic events within CO are less certain. We will use single-channel kinetics and phi-value analysis to probe the interior of AChR gating and illuminate the ultra-fast protein rearrangements within this reaction. So far, results show that AChRs change from C-to-O in 4 steps. The first amino acids to move are not at the transmitter binding sites but in a distant membrane domain linker that joins the M2 and M3 helices of the subunit. Further, the unlocking of a double-gate in M2 (all subunits) occurs in the final 2 gating activation steps. Most side chain gating movements are 'resettling' events that have only local energetic consequences. We will investigate two new hypotheses for AChR gating: 1) communication between the binding sites and the gate is not by a structural-mechanical process but, rather, by the vibrational entropy of the entire backbone, and 2) allosteric communication commences with low-affinity binding of the agonist to the resting receptor.