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个膜蛋白结构被高分辨率地解析出来。因为 α-螺旋膜蛋白占基因组序列的约30%，从氨基酸预测 对这些蛋白质的三维结构进行测序是一个重要的目标。这种预测需要 理解两个基本问题：SecY/Sec 61的MP生物组装机制 （translocon）复合物以及MP在其天然脂双层环境中的物理稳定性原理。 本提案的具体目标涉及这两个问题的以下方面： 它决定了一种多肽 片段通过Sec 61复合物作为跨膜整合到内质网膜中 螺旋。这项工作将扩大第一个草案'生物'疏水性规模获得使用体外系统 基于模型蛋白到微粒体中的共翻译插入。(2)深入了解translocon 功能使用分子动力学模拟的SecY复合物从M.詹氏，其中 最近已经确定了晶体结构。这些模拟将允许操纵 在双层环境中的易位子结构作为学习易位子如何可以打开的手段， 接近释放TM螺旋进入双层。(3)建立了基于实验的界面疏水性 描述多肽片段与形成的双层界面区域相互作用的尺度 来自ER脂质。这很重要，因为易位子，大概与脂质双层， 区分双层的烃核心和界面区域。(4)澄清物理基础 用于translocon辅助插入（1）短TM螺旋（~ 12个氨基酸）和（2）模型 来自KvAP电压门控K+通道的S4螺旋电压传感器肽。获得的信息将有助于 我们知道如何预测不寻常的膜蛋白，如CIC的拓扑和结构， 氯离子通道