Identifying the Molecular Determinants of Ferredoxin Transport into the Periplasm of Pectobacterium spp.

Fe3+的吸收对大多数细菌的生长和生存至关重要。然而，由于Fe3+的水溶性较差，在生理条件下其在胞外介质中的浓度较低，因此被动扩散不利于细菌对铁的吸收。为了克服这一点，革兰氏阴性细菌从含铁的底物和宿主蛋白质中捕获铁。这是通过复杂的主动运输机制实现的。植物病原菌的铁还蛋白摄取系统(FUS)，细小杆菌以宿主铁还蛋白为靶标，结合在细菌细胞表面，并通过外膜运输蛋白FusA进入周质。FUS系统中有三种蛋白质参与了铁氧还蛋白的摄取和加工：FusA和FusB，FusC，已被证明在周质中处理铁氧还蛋白。该项目涉及铁氧还蛋白的摄取，因此重点关注FusA和FusB。结构和生物物理数据提供了对所涉及的FUS蛋白质的洞察，然而，仍然有一些重要的问题，本项目将使用计算方法来解决。表征过程被分解成有重点的目标：1.建立任何替代X-射线结构所提出的Fusa-Ferredox2构型。确定FusA插塞域在与铁氧还蛋白3相互作用中的作用。表征铁氧还蛋白通过Fusa的途径，确定铁氧还蛋白在易位中展开的程度4。为FusB生成一个模型，探索它在从FusA中移除Plug结构域的可能性

The uptake of Fe3+ is vital for the growth and survival of most bacteria. However, due to the poor water solubility of Fe3+, its concentration is low in the extracellular medium under physiological conditions, consequently passive diffusion is impractical for iron uptake by bacteria. To overcome this, Gram-negative bacteria capture iron from iron-containing substrates and host proteins. This is achieved through sophisticated active transport mechanisms. The Ferredoxin Uptake System (Fus) from the plant pathogen, Pectobacterium targets host ferredoxin (a small iron-sulphur cluster containing protein), binding it at the bacterial cell surface and transporting it through the outer-membrane transport protein FusA into the periplasm. Three proteins of the Fus system involved in uptake and processing of ferredoxin have been identified; FusA and FusB which mediate uptake, FusC which has been shown to process ferredoxin in the periplasm. This project is concerned with ferredoxin uptake, and is therefore focussed on FusA and FusB. Structural and biophysical data have provided insight into the Fus proteins involved, however, there remain some important questions, which this project will address, suing computational methods. The characterisation process has been broken down into focused objectives:1. Establish any alternative FusA-ferredoxin configurations to that proposed by x-ray structure2. Identify the role of the FusA plug domain in interactions with ferredoxin3. Characterise the passage of ferredoxin through FusA, establishing the extent of unfolding in ferredoxin in translocation4. Generate a model for FusB, exploring the possibility of it playing a role in removing the plug domain from FusA