Membrane Protein Folding and Assembly

膜蛋白折叠和组装

• 批准号: 7586269
• 负责人: STEPHEN H. WHITE
• 金额: $ 35.2万
• 依托单位: UNIVERSITY OF CALIFORNIA-IRVINE
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7586269
• 关键词: Accounting; Address; Amino Acid Sequence; Amino Acids; Biological; Canis familiaris; Chloride Channels; Code; Communication; Complex; Data; Endoplasmic Reticulum; Environment; Free Energy; Genomics; Goals; Hydrocarbons; Hydrophobicity; In Vitro; Learning; Lipid Bilayers; Lipids; Membrane; Membrane Proteins; Methanococcus; Methodology; Microsomes; Modeling; Pancreas; Peptides; Potassium Channel; Proteins; Resolution; Shunt Device; Side; Signal Transduction; Structure; System; Testing; Voltage-Gated Potassium Channel; Work; base; genome sequencing; in vivo; insight; interfacial; mathematical algorithm; molecular dynamics; polypeptide; protein complex; protein folding; protein structure; research study; seal; sensor; simulation; three dimensional structure; voltage

Only 75 membrane protein structures had been solved to high resolution by the close of 2003. Because alpha-helical membrane proteins account for ~30% of genome sequences, predicting from amino acid sequence the three-dimensional structures of these proteins is an important goal. Such predictions require understanding two fundamental issues: mechanisms of the biological assembly of MPs by the SecY/Sec61 (translocon) complex and the principles of the physical stability of MPs in their natural lipid bilayer milieu. The specific aims of this proposal address aspects of both issues as follows: (1) Decipher the "code" embedded in membrane protein amino acid sequences that determines whether or not a polypeptide segment is integrated into the endoplasmic reticulum membrane by the Sec61 complex as a transmembrane helix. This work will expand a first draft 'biological' hydrophobicity scale obtained using an in vitro system based upon cotranslational insertion of model proteins into microsomes. (2) Gain insights into translocon function using molecular dynamics simulations of the SecY complex from M.jannaschii, for which the crystallographic structure has been determined recently. These simulations will allow manipulation of the translocon structure in the bilayer environment as a means of learning how the translocon may open and close to release TM helices into the bilayer. (3) Establish an experiment-based interracial hydrophobicity scale for describing the interactions of polypeptide segments with the interface regions of bilayers formed from ER lipids. This is important because the translocon, presumably in concert with the lipid bilayer, distinguishes between the bilayer's hydrocarbon core and interfacial regions. (4) Clarify the physical basis for translocon-assisted insertion into membranes of (1) short TM helices (-12 amino acids) and (2) a model S4 helix voltage-sensor peptide from the KvAP voltage-gated K+ channel. The information obtained will help us understand how to predict the topolgy and structure of unusual membrane proteins, such as the CIC chloride channel.

到 2003 年底，只有 75 个膜蛋白结构被解析为高分辨率。因为 根据氨基酸预测，α-螺旋膜蛋白约占基因组序列的 30% 对这些蛋白质的三维结构进行测序是一个重要的目标。此类预测需要 了解两个基本问题： SecY/Sec61 的 MP 生物组装机制 （易位子）复合物和 MP 在其天然脂质双层环境中的物理稳定性原理。 该提案的具体目标是解决这两个问题的以下方面： (1) 破译“代码” 嵌入膜蛋白氨基酸序列中，决定多肽是否存在 该片段通过 Sec61 复合物作为跨膜整合到内质网膜中 螺旋。这项工作将扩展使用体外系统获得的“生物”疏水性量表初稿 基于模型蛋白共翻译插入微粒体。 (2) 深入了解易位子 使用来自 M.jannaschii 的 SecY 复合体的分子动力学模拟来计算函数，其中 最近确定了晶体结构。这些模拟将允许操纵 双层环境中的易位子结构作为学习易位子如何打开和释放的一种手段 接近将TM螺旋释放到双层中。 (3) 建立基于实验的界面疏水性 用于描述多肽片段与形成的双层界面区域相互作用的量表 来自 ER 脂质。这很重要，因为易位子可能与脂质双层协同作用， 区分双层的碳氢化合物核心和界面区域。 (4)明确物理基础 用于易位子辅助插入 (1) 短 TM 螺旋（-12 个氨基酸）和 (2) 模型的膜 来自 KvAP 电压门控 K+ 通道的 S4 螺旋电压传感器肽。获得的信息将有帮助 我们了解如何预测不寻常膜蛋白的拓扑和结构，例如 CIC 氯离子通道。