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

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 structure
2. Identify the role of the FusA plug domain in interactions with ferredoxin
3. Characterise the passage of ferredoxin through FusA, establishing the extent of unfolding in ferredoxin in translocation
4. Generate a model for FusB, exploring the possibility of it playing a role in removing the plug domain from FusA