LONG RANGE RADICAL INITIATION IN E COLI RIBONUCLEOTIDE REDUCTASE

大肠杆菌核糖核苷酸还原酶中的长程自由基引发

• 批准号: 7420493
• 负责人: JOANNE STUBBE
• 金额: $ 0.9万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7420493
• 关键词: allosteric site; binding sites; catalyst; cofactor; cysteine; electron transport; housing; iron; measurement; model; nucleotides; proteins; pyrophosphates; reduction; ribonucleotide reductase; thinking

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. E.coli ribonucleotide reductase catalyzes the conversion of nucleoside diphosphates (NDP) to deoxynucleoside diphosphates. The active protein is composed of two homodimeric subunits (R1 and R2) thought to form a 1:1 complex. R1 binds the NDP substrates, houses the essential cysteines required for catalysis and the binding sites for the allosteric effectors that govern substrate specificity and turnover rates. R2 harbors the essential di-iron tyrosyl radical cofactor on residue 122 (Y?). A major unresolved issue is the mechanism of radical initiation: how the tyrosyl radical (Y?) in R2 generates a transient thiyl radical (C439?) in R1 required for nucleotide reduction. The current model for the radical initiation process involves a specific electron transfer pathway, which traverses a distance of 3.5 nm, derived from a docking model of the R1 and R2 structures, but a substantial part of the pathway is not apparent from the available structural information. A measurement of the distance between Y122 and C439 was imperative to establish the radical initiation model.

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子弹和调查员（PI）可能已经从其他NIH来源获得了主要资金，因此可以在其他清晰的条目中代表。列出的机构适用于该中心，这不一定是调查员的机构。大肠杆菌核糖核苷酸还原酶催化核苷二磷酸（NDP）转化为脱氧核苷二磷酸。活性蛋白质由两个同二聚体亚基（R1和R2）组成，认为形成了1：1复合物。 R1结合NDP底物，容纳催化所需的基本半胱氨酸以及控制底物特异性和周转率的变构效应子的结合位点。 R2在残基122（Y？）上携带必需的Di-Iron酪酶自由基辅助因子。一个主要的未解决的问题是自由基起始的机制：R2中的酪酶自由基（Y？）如何在核苷酸还原所需的R1中产生瞬时硫基自由基（C439？）。自由基启动过程的当前模型涉及特定的电子传递途径，该途径横穿3.5 nm的距离，该距离源自R1和R2结构的对接模型，但是从可用的结构信息中可以看出，该途径的很大一部分并不明显。必须测量Y122和C439之间的距离，必须建立自由基的启动模型。