Structural analysis of the siroheme biosynthetic enzyme CysG, a central player in sulfur metabolism

硫代谢中的核心角色西罗血红素生物合成酶 CysG 的结构分析

基本信息

批准号：
1904612
负责人：
Elizabeth Stroupe
金额：
$ 39万
依托单位：
Florida State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-15 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904612&HistoricalAwards=false
关键词：
Structural analysis siroheme biosynthetic enzyme

项目摘要

Heme is the iron-containing molecule that allows hemoglobin to carry oxygen in blood. Heme also plays many other important biochemical functions in cells. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Elizabeth Stroupe at Florida State University to study a special form of heme (called siroheme). Siroheme helps chemically transform environmental sulfur or nitrogen compounds to biologically usable forms using microbes. This research topic is of particular importance because environmental pollution in the form of toxic sulfur byproducts from commercial pig farms has become problematic due to recent flooding in the southern United States. Dr. Stroupe is studying a key enzyme (CysG) made from two bacteria in order to determine the basic science of siroheme formation. By knowing how siroheme is formed, scientists may improve upon the bio-remediation of toxic sulfur compounds. The project trains diverse groups of undergraduate and graduate students in molecular structure determinations and follows the biochemical activity of enzymes at various stages of reaction. Dr. Stroupe and her students impart an appreciation for the role that organic chemistry plays in biology to middle and high school students through the SCIGirls and Florida's Next Generation Science Standards outreach programs.Proteobacteria use a single gene product (CysG) to synthesize siroheme. CsyG is the product of a gene fusion event between a methyltransferase (CysG-A) and a bifunctional dehydrogenase/ferrochelatase (CysG-B). The mechanisms for CysG-B's bifunctionality and its alternative function as a cobaltchelatase are unknown. Other organisms use three distinct enzymes for siroheme synthesis, including the CysG-B homolog SirC, which is a monofunctional dehydrogenase. X-ray crystallography, biochemical analysis, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) are applied to dissect the underlying mechanisms for the last two steps of siroheme synthesis. The questions addressed by this project include how bifunctional active sites in CysG-B catalyze dehydrogenation and metal chelation and how chelatase discriminates between iron and cobalt to make siroheme. Researchers also ask how CysG-B functions as a bifunctional dehydogenase/ferrochelatase when SirC, a homologous enzyme, only functions as a dehydrogenase.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

血红素是一种含铁分子，可以让血红蛋白在血液中携带氧气。血红素还在细胞中发挥许多其他重要的生化功能。凭借该奖项，化学系的生命过程化学项目正在资助佛罗里达州立大学的 Elizabeth Stroupe 博士研究一种特殊形式的血红素（称为西罗血红素）。 Siroheme 有助于利用微生物将环境中的硫或氮化合物化学转化为生物可用的形式。该研究课题特别重要，因为由于美国南部最近的洪水，商业养猪场产生的有毒硫副产品形式的环境污染已成为问题。 Stroupe 博士正在研究一种由两种细菌制成的关键酶 (CysG)，以确定西罗血红素形成的基础科学。通过了解西罗血红素是如何形成的，科学家可以改进有毒硫化合物的生物修复。该项目对不同群体的本科生和研究生进行分子结构测定方面的培训，并跟踪酶在反应各个阶段的生化活性。 Stroupe 博士和她的学生通过 SCIGirls 和佛罗里达州下一代科学标准推广计划向中学生和高中生传授有机化学在生物学中所发挥的作用。变形菌使用单基因产物 (CysG) 来合成西罗血红素。 CsyG 是甲基转移酶 (CysG-A) 和双功能脱氢酶/铁螯合酶 (CysG-B) 之间基因融合事件的产物。 CysG-B 的双功能及其作为钴螯合酶的替代功能的机制尚不清楚。其他生物体使用三种不同的酶来合成西罗血红素，包括 CysG-B 同源物 SirC，它是一种单功能脱氢酶。应用 X 射线晶体学、生化分析和傅里叶变换离子回旋共振质谱 (FT-ICR MS) 来剖析西罗血红素合成最后两个步骤的基本机制。该项目解决的问题包括 CysG-B 中的双功能活性位点如何催化脱氢和金属螯合，以及螯合酶如何区分铁和钴来制造西罗血红素。研究人员还询问，当同源酶 SirC 仅充当脱氢酶时，CysG-B 如何充当双功能脱氢酶/铁螯合酶。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。