TonB-dependent transport across the outer membrane

TonB 依赖性跨外膜运输

• 批准号: 8799321
• 负责人: KATHLEEN POSTLE
• 金额: $ 32.95万
• 依托单位: PENNSYLVANIA STATE UNIVERSITY, THE
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8799321
• 关键词: Active Biological Transport; Address; Affinity; Antibiotics; Binding; Biochemical Genetics; Biological Availability; Biological Models; British Columbia; Cell membrane; Chelating Agents; Colicin B; Collaborations; Complex; Couples; Cytoplasm; Development; Diffuse; Diffusion; Engineering; Environment; Escherichia coli; Event; Foundations; Francisella; Goals; Gram-Negative Bacteria; Harvest; Health; In Vitro; Ions; Iron; Knowledge; Lead; Length; Ligand Binding; Ligands; Lipids; Mechanics; Mediating; Membrane; Membrane Proteins; Membrane Transport Proteins; Molecular; Movement; Nutrient; Periplasmic Binding Proteins; Phase; Plasmids; Play; Process; Proteins; Proton-Motive Force; Resources; Role; Side; Siderophores; Signal Transduction; Spheroplasts; Staging; Structure; System; Toxin; Transmembrane Domain; Universities; Variant; Vesicle; Vesicle Transport Pathway; Virulence Factors; base; beta barrel; cell growth; colicin; crosslink; disulfide bond; in vivo; nanodisk; novel; pathogen; periplasm; porin; reconstitution; small molecule

 DESCRIPTION (provided by applicant): The outer membranes of Gram-negative bacteria are barriers to diffusion of many important nutrients such as iron-siderophores into the periplasmic space. To circumvent these limitations, active transporters with very high affinities for their transport ligands are located in the outer membrane. However the outer membrane lacks conventional energy resources of sufficient ion gradients or access to ATP. Instead, energy for active transport across the outer membrane is transduced from the cytoplasmic membrane proton motive force by three integral cytoplasmic membrane proteins, TonB-ExbB-ExbD. ExbB/D harvest the proton motive force and transmit it to TonB, which directly contacts the outer membrane transporter. The exact mechanism of energy transduction to the outer membrane transporter is unknown. Our long- term goal is to understand the mechanism of TonB-dependent energy transduction between the cytoplasmic and outer membranes using Escherichia coli as the model system. Because of the role it plays in iron acquisition the TonB system is a virulence factor for many Gram-negative pathogens. Our long-term goal is to understand the mechanism of TonB-dependent energy transduction between the cytoplasmic and outer membranes of Escherichia coli. Past in vitro studies have characterized binding of TonB periplasmic domains (lacking the essential transmembrane domain) to purified transporters. To date, actual transport has not been demonstrated. We will identify the residue-specific energy-dependent interactions that occur between active full-length TonB and the outer membrane transporter FepA during transport in vivo. This knowledge will be used to evaluate in vitro interactions between FepA and active full-length TonB. We will also identify unknown proteins in the TonB system and characterize the role they play.

 描述（由申请人提供）：革兰氏阴性菌的外膜是许多重要营养物质（如铁-铁载体）扩散到周质间隙的屏障。为了规避这些限制，与其转运配体具有非常高亲和力的活性转运蛋白位于外膜中。然而，外膜缺乏足够的离子梯度或进入ATP的常规能量资源。相反，跨外膜主动运输的能量是由三种完整的细胞质膜蛋白TonB-ExbB-ExbD从细胞质膜质子动力转换而来的。ExbB/D收集质子动力并将其传输到直接接触外膜转运蛋白的TonB。能量传递到外膜转运蛋白的确切机制尚不清楚。我们的长期目标是利用大肠杆菌作为模型系统，了解细胞质和外膜之间TonB依赖性能量转导的机制。由于TonB系统在铁获取中的作用，它是许多革兰氏阴性病原体的毒力因子。我们的长期目标是了解大肠杆菌细胞质和外膜之间TonB依赖性能量转导的机制。过去的体外研究已经表征了TonB周质结构域（缺乏必需的跨膜结构域）与纯化的转运蛋白的结合。到目前为止，实际运输尚未得到证明。我们将确定在体内运输过程中活性全长TonB和外膜转运蛋白FepA之间发生的残基特异性能量依赖性相互作用。这些知识将用于评价FepA和活性全长TonB之间的体外相互作用。我们还将识别TonB系统中的未知蛋白质，并描述它们所起的作用。