The function of a conserved cysteine pair in SRP54

SRP54 中保守的半胱氨酸对的功能

• 批准号: 6558001
• 负责人: Douglas M. Freymann
• 金额: $ 14.87万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-05-01 至 2005-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6558001
• 关键词: X ray crystallography; biochemistry; cysteine; disulfide bond; guanosinetriphosphatases; hydrolysis; intermolecular interaction; oxidation reduction reaction; protein purification; protein signal sequence; protein structure function; ribonucleoproteins; thermodynamics

DESCRIPTION (provided by applicant): The signal recognition particle (SRP) is an evolutionarily conserved ribonucleoprotein that targets 'nascent secreted and membrane proteins to the endoplasmic reticulum. The SRP plays a role in the secretion of numerous clinically relevant proteins, and an understanding of its structural and functional mechanisms is of fundamental importance for understanding the biology of the co-translational secretion pathway in the the eukaryotic cell. One protein of the SRP, termed SRP54, integrates two key activities of the particle - the recognition of the N-terminal signal peptide, and the GTP-dependent formation of a targeting complex with the SRP receptor (SR) at the membrane. Crystal structures of the signal recognition and GTPase domains of the prokaryotic homolog of SRP54 allow the construction of a three-dimensional model of the eukaryotic protein. On this basis a pair of cysteine residues that are universally conserved in the eukaryotic SRP54 can be mapped to opposite sides of the GTPase active site pocket. The functional role of these two residues is completely unknown. We hypothesize that the two cysteines, perhaps regulated by other factors such as the cellular redox state, modulate or alter the GTPase cycle of the SRP. As a first step in this work, therefore, we aim to characterize the behavior of the GTPase domain of SRP54 with respect to redox and disulfide states. Subsequent work is directed towards understanding the role of the cysteines in vivo, with a long term goal of understanding the structural basis for their function and determining their biological significance. Although the project is somewhat high risk, it has the potential to reveal an unanticipated and significant new regulatory mechanism of the SRP.

描述(申请人提供)：信号识别颗粒(SRP)是一种进化上保守的核糖核蛋白，以新生分泌和膜蛋白为靶点进入内质网。SRP在许多临床相关蛋白的分泌中发挥作用，了解其结构和功能机制对于理解真核细胞中共翻译分泌途径的生物学具有重要意义。SRP的一种蛋白质，称为SRP54，整合了该颗粒的两个关键活性-识别N-末端信号肽，以及依赖GTP与膜上的SRP受体(SR)形成靶向复合体。SRP54原核同源物的信号识别和GTPase结构域的晶体结构允许构建真核蛋白质的三维模型。在此基础上，真核生物SRP54中普遍保守的一对半胱氨酸残基可以被定位到GTP酶活性部位口袋的相反侧。这两个残基的功能作用完全未知。我们推测，这两种半胱氨酸可能受到其他因素的调节，如细胞的氧化还原状态，调节或改变SRP的GTP酶周期。因此，作为这项工作的第一步，我们的目标是表征SRP54的GTPase结构域在氧化还原和二硫键状态下的行为。随后的工作旨在了解半胱氨酸在体内的作用，长期目标是了解其功能的结构基础并确定其生物学意义。尽管该项目具有一定的高风险，但它有可能揭示出SRP一个意想不到的重要新监管机制。