ION CHANNEL PROTEINS IN MEMBRANES

膜中的离子通道蛋白

• 批准号: 6456770
• 负责人: ANDREW POHORILLE
• 金额: $ 27.32万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6456770
• 关键词: biomedical resource; cardiovascular system; computers; congenital disorders; health care; informatics; proteins; statistics /biometry; technology /technique

Our research focuses on the Influenza-A M2 protein, a small homotetrameric, voltage-gated ion channel. Each monomer is 97 amino acids in length, and contains a single transmembrane (TM) domain of 19 residues. This channel is very effective in transporting protons and screens out other types of ions. Although no high resolution structural data for M2 are available to date, recent NMR and CD studies of this protein in phospholipid bilayers strongly suggest that the TM region is alpha-helical and has the quaternary structure of a 4-helix bundle. The mechanisms of channel gating by M2 is also currently unknown. There are two main hypotheses regarding gating of protons. One considers the formation of a water wire through the channel and the ability of such a structure to transfer protons through the channel. The second hypothesis is based on a proton shuttle mechanism mediated by four intraluminal histidine residues forming the gate. Our aim in this study has been to elucidate the gating mechanism of M2, and to demonstrate the stability of a structural model of M2 in an explicit water-phospholipid bilayer system. We have performed several molecular dynamics simulations, each consisting of a trajectory at least one nanosecond long. Each simulation corresponded to a different protonation state of the histidine residues in the gate. The unprotonated and single protonated forms involved in the proton shuttle mechanism were found to be stable over the full length of the trajectory. Furthermore, the orientation of water molecules inside the channel was conducive to effective proton transfer. In contrast, the form in which all four histidine residues are protonated, required in the water-wire mechanism, was unstable and disassociated on a timescale of 400 - 700 ps. Our results demonstrate that proton shuttle involving histidine residues of the protein is the most likely mechanism of proton transport in the M2 channel.

我们的研究重点是甲型流感 M2 蛋白，一种小型流感病毒 M2 蛋白。 同源四聚体，电压门控离子通道。 每个单体有97个氨基 长度为 19 个酸，包含一个跨膜 (TM) 结构域 残留物。 该通道在传输质子和 筛选出其他类型的离子。 虽然没有高分辨率 迄今为止，最新的 NMR 和 CD 均提供了 M2 的结构数据 对磷脂双层中这种蛋白质的研究强烈表明 TM区域是α螺旋并且具有a的四级结构 4-螺旋束。 M2 的通道门控机制也 目前未知。 关于门控有两个主要假设 质子。 人们认为通过水线形成 通道以及这种结构传输质子的能力 通过通道。 第二个假设是基于质子 由四个腔内组氨酸残基介导的穿梭机制 形成门。 我们这项研究的目的是阐明 M2 的门控机制，并证明了 a 的稳定性 显式水-磷脂双层中 M2 的结构模型 系统。 我们进行了多次分子动力学模拟， 每个都由至少一纳秒长的轨迹组成。 每个 模拟对应于不同的质子化状态 门中的组氨酸残基。 非质子化和单一 发现了参与质子穿梭机制的质子化形式 在整个轨迹长度上保持稳定。 此外， 通道内水分子的定向有利于 有效的质子转移。 相比之下，所有四种形式 组氨酸残基被质子化，这是水线中所需的 机制，在 400 - 700 的时间尺度上不稳定且分离 附： 我们的结果表明质子穿梭涉及组氨酸 蛋白质的残基是质子最可能的机制 M2 通道中的传输。