Structure and Function of IscA, a Potential Iron Delivery Protein for Iron-Sulfur Cluster Assembly

IscA（一种用于铁硫簇组装的潜在铁输送蛋白）的结构和功能

• 批准号: 0416537
• 负责人: Huangen Ding
• 金额: $ 47.98万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0416537&HistoricalAwards=false
• 关键词: Structure; Function; IscA; Potential; Iron

Iron-sulfur clusters are one of the most ubiquitous redox co-factors in biology. Throughout evolution, iron-sulfur clusters have become integral part of diverse physiological processes such as energy conversion, sugar metabolism, nitrogen fixation, heme and biotin biosynthesis, DNA synthesis and DNA repair, and regulation of gene expression. At least six proteins (IscS, IscU, IscA, HscB, HscA and Ferredoxin) encoded by a gene cluster iscSUA-hscBA-fdx have been identified as essential for the general biogenesis of iron-sulfur clusters in bacteria. The homologs of the six proteins have also been found in eukaryotic organisms, indicating that the iron-sulfur cluster assembly mechanism is highly conserved. It has been shown that IscS, a cysteine desulfurase, provides sulfur for iron-sulfur clusters, and that IscU is a scaffold for the IscS-mediated assembly of iron-sulfur clusters and eventually transfers iron-sulfur clusters to target proteins. However, the iron donor for iron-sulfur clusters largely remains elusive. This project aims to test a hypothesis that the primary function of IscA is to recruit intracellular iron and deliver iron for the assembly of iron-sulfur clusters in IscU, and that the IscA-mediated iron transfer to IscU is coordinated through the protein-protein interactions. The research has two specific aims: 1) To define the iron binding properties of IscA by combining the biochemical, biophysical and X-ray crystallographic approaches to identify the amino acid residues that are important for the iron binding and to determine the redox properties of the iron center. 2) To investigate the mechanism of iron transfer from IscA to the iron-sulfur clusters in IscU by exploring the protein-protein interactions of IscA with IscU and IscS. The results will provide fundamental knowledge on the general biogenesis of iron-sulfur clusters, a process that is conserved from bacteria to humans. In addition, understanding iron delivery for the biogenesis of iron-sulfur clusters will offer the molecular details on how intracellular iron may be utilized in other biological processes.Broader Impacts: The project is expected to attract and retain high quality graduate and undergraduate students. The students will not only learn the multidisciplinary methodology to conduct the proposed research, but also develop the attitude crucial to their future career in academia or industries through vigorous research activities. Special efforts will be taken to recruit highly motivated minority and woman graduate students to the research group. The research projects will further be integrated into the biochemistry courses that the PI and Co-PI have been teaching at their institution, and should greatly benefit the institutional biochemistry curricula.

铁-硫团簇是生物中最普遍的氧化还原辅助因子之一。在整个进化过程中，铁-硫簇已经成为能量转换、糖代谢、固氮、血红素和生物素生物合成、DNA合成和DNA修复以及基因表达调控等多种生理过程中不可或缺的一部分。由iscSUA-hscBA-FDX基因簇编码的至少6种蛋白质(IscS、IscU、IscA、HscB、HscA和铁氧还蛋白)已被鉴定为细菌中铁-硫簇的一般生物发生所必需的。这六种蛋白质的同源物也在真核生物中被发现，表明铁-硫簇组装机制是高度保守的。研究表明，ISCS是一种半胱氨酸脱硫酶，为铁-硫簇提供硫，而ISCU是ISCS介导的铁-硫簇组装的支架，最终将铁-硫簇转移到靶蛋白上。然而，铁硫团簇的铁供给者在很大程度上仍然难以捉摸。本项目旨在验证一种假设，即ISCA的主要功能是募集细胞内的铁并为ISCU中的铁-硫簇的组装输送铁，并且ISCA介导的铁向ISCU的转移是通过蛋白质-蛋白质相互作用来协调的。本研究有两个具体目的：1)通过结合生化、生物物理和X射线结晶学的方法来确定ISCA的铁结合性质，以确定对铁结合至关重要的氨基酸残基，并确定铁中心的氧化还原性质。2)通过研究ISCA与ISCU和ISCS的蛋白质-蛋白质相互作用，探讨ISCA向ISCU中铁-硫簇转移的机制。这些结果将提供有关铁-硫团簇一般生物发生的基础知识，这一过程从细菌到人类都是保守的。此外，了解铁在铁-硫簇生物发生中的传递将提供细胞内铁如何被用于其他生物过程的分子细节。广泛的影响：该项目预计将吸引和留住高质量的研究生和本科生。学生不仅将学习进行拟议研究的多学科方法论，还将通过积极的研究活动发展对他们未来在学术界或行业的职业至关重要的态度。将作出特别努力，招募积极进取的少数族裔和女研究生加入研究小组。这些研究项目将进一步纳入国际和平研究所和联合国际组织在其机构教授的生物化学课程，并将极大地有利于该机构的生物化学课程。