Biosynthesis and Physiology of Vitamin B12 in Prokaryotes

原核生物维生素 B12 的生物合成和生理学

基本信息

批准号：
7361621
负责人：
Michiko E. Taga
金额：
$ 9万
依托单位：
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-12-01 至 2009-11-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/7361621
关键词：
5,6-dimethylbenzimidazole Alfalfa Amino Acids Anabolism Anaerobic Bacteria Bacteria Bacterial Genome Biochemical Biochemical Genetics Bioinformatics Biological Process Catalysis Cells Clostridium perfringens DNA Damage DNA biosynthesis Dementia Diet Disease Disruption Elderly Enterobacteriaceae Enzymes Fabaceae Flavin Mononucleotide Flavins Genes Genetic Genome Goals Hematological Disease Homologous Gene Human Icterus Individual Infection Knowledge Laboratories Lead Ligands Mediating Melilotus Methods Mixed Function Oxygenases Molecular Nitrogen Organism Oxygen Pathogenesis Pathway interactions Phenotype Physiological Physiology Plague Production Prokaryotic Cells Purines Reaction Research Research Personnel Riboflavin Ribonucleotide Reductase Role Salmonella typhimurium Sinorhizobium meliloti Spectrophotometry Stress Structure Symbiosis Techniques Vitamin B 12 Vitamins Walkers Work deprivation insight microorganism mutant novel pathogenic bacteria post-doctoral training professor purine response sugar

项目摘要

DESCRIPTION (provided by applicant): Vitamin B12 is a critical component of the human diet. B12 deficiency, which plagues over 20% of elderly individuals, can cause hematological disorders, jaundice, loss of coordination, and dementia. Understanding how this vitamin is synthesized may contribute to the overall knowledge and treatment of B12-related disease. Unlike all other vitamins, B12 is synthesized exclusively by microorganisms. In some pathogenic bacteria, B12 is utilized specifically during infection of the host. Therefore, studying the physiology of B12 in bacteria could lead to insights about pathogenesis. Until recently, the enzymes responsible for the production of the "lower ligand" of B12, 5,6-dimethylbenzimidazole (DMB), were unknown. We recently identified BluB, an enzyme that catalyzes the production of DMB in the symbiotic nitrogen fixing bacterium Sinorhizobium meliloti. The bluB mutant of S. meliloti is severely impaired in establishing a nitrogen-fixing symbiosis with its legume host, alfalfa. Our structural and biochemical analyses demonstrated that BluB catalyzes the oxygen-dependent transformation of flavin mononucleotide (FMN) to DMB. The proposed work will seek to identify the detailed reaction mechanism of this unique transformation. Putative homologs of bluB exist in numerous bacterial genomes, suggesting that BluB has a ubiquitous role in DMB biosynthesis. However, a separate DMB biosynthetic pathway that does not use FMN as a precursor exists in anaerobic bacteria, and the enzymes involved in this pathway have not been identified. The anaerobic DMB biosynthetic pathway will be investigated by genetic, bioinformatic, and biochemical approaches using the techniques developed in studying BluB. Additionally, the physiological response to B12 deprivation in S. meliloti will be analyzed. In S. meliloti, an altered exopolysaccharide is produced in response to B12 deprivation, and this response is caused by DNA damage. The structure, regulatory mechanism, and physiological relevance of the DNA damage-induced altered exopolysaccharide will be explored. Together, these studies will contribute to the overall understanding of B12 biosynthesis and the function of B12 in bacteria-host interactions.

描述（由申请人提供）：维生素B12是人类饮食的关键组成部分。 B12缺乏症，困扰着20％以上的老年人，会导致血液学疾病，黄疸，协调丧失和痴呆症。了解这种维生素如何合成可能有助于与B12相关疾病的整体知识和治疗。与所有其他维生素不同，B12仅由微生物合成。在某些致病性细菌中，B12在宿主感染期间专门用于使用。因此，研究B12在细菌中的生理可能会导致有关发病机理的见解。直到最近，尚不清楚负责生产B12的“下配体”的酶（DMB）。我们最近确定了Blub，这是一种催化DMB在共生氮固定细菌中的酶的酶。 Meliloti的Blub突变体与其豆类宿主Alfalfa建立氮固定共生时受到严重损害。我们的结构和生化分析表明，BLUB催化黄素单核苷酸（FMN）催化氧依赖性转化为DMB。拟议的工作将寻求确定这种独特转化的详细反应机制。 Blub的推定同源物存在于许多细菌基因组中，这表明Blub在DMB生物合成中具有无处不在的作用。但是，尚未鉴定出一种不使用FMN作为前体的DMB生物合成途径，该途径尚未使用FMN作为前体，并且尚未鉴定出参与该途径的酶。厌氧DMB生物合成途径将通过研究BLUB中开发的技术来研究遗传，生物学和生化方法。另外，将分析对梅洛蒂（S. meliloti）中B12剥夺的生理反应。在Meliloti链球菌中，响应B12剥夺而产生的外多糖改变了，这种反应是由DNA损伤引起的。将探索DNA损伤引起的改变外多糖改变的结构，调节机制和生理相关性。总之，这些研究将有助于对B12生物合成的总体理解以及B12在细菌宿主相互作用中的功能。