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个膜蛋白质结构被解析到高分辨率。因为 从氨基酸预测，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。这样的预测需要 理解两个基本问题：SecY/Sec61对MPS的生物组装机制 (转运子)复合体和MPS在其天然脂双层环境中的物理稳定性的原理。 这项提案的具体目标涉及以下两个问题：(1)破译“密码” 嵌入在膜蛋白中的氨基酸序列，决定了多肽是否 片段通过Sec61复合体以跨膜的形式整合到内质网膜中 螺旋。这项工作将扩展使用体外系统获得的初稿的生物疏水性标尺 基于将模型蛋白质共翻译插入微生物体。(2)深入了解易位 使用分子动力学模拟来自Jannaschii的SecY复合体的功能，对于该复合体， 最近已经确定了晶体结构。这些模拟将允许对 双层环境中的转运子结构，作为研究转运子如何开放和 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 描述多肽片段与形成的双层的界面区域相互作用的标尺 来自急诊室的脂类。这一点很重要，因为转运子可能与脂双层结合， 区分双层的碳氢化合物核心和界面区域。(四)理清物质基础 用于(1)短TM螺旋(-12个氨基酸)和(2)模型的转位辅助插入膜 S4螺旋电压敏感肽来自KvAP电压门控K+通道。所获得的信息将有所帮助 我们了解如何预测不寻常的膜蛋白的拓扑和结构，如CIC 氯离子通道。