Award details

A protein secretion portal at the hyphal tips of Streptomyces coelicolor?

Reference	BB/F002947/1
Principal Investigator / Supervisor	Professor Tracy Palmer
Co-Investigators / Co-Supervisors
Institution	University of Dundee
Department	School of Life Sciences
Funding type	Research
Value (£)	357,328
Status	Completed
Type	Research Grant
Start date	21/01/2008
End date	20/07/2011
Duration	42 months

Abstract

The Tat protein transport system functions to export folded proteins across the bacterial cytoplasmic membrane. Proteins are targeted to the Tat machinery by N-terminal signal peptides that harbour an almost invariant twin arginine motif. Our studies have shown that the Tat pathway is a major route of protein export in the Gram positive soil organism Streptomyces coelicolor. EGFP-tagging of the essential TatB protein of the S. coelicolor Tat system at single copy showed that this protein is localized at the tips of the vegetative hyphae, This is therefore analagous to tip-localized secretion of proteins previously observed for filamentous fungi. In this application we aim to address whether: 1. Other components of the Tat machinery also show tip-localization, and whether tip-localization is dependent upon a functional Tat system; 2. Whether other exporters and uptake systems also show tip localization; 3. Whether new Tat subunits are added directly to the hyphal tip or if they are synthesized elsewhere and subsequently accumulate at the tip. 4. The mechanism by which the Tat machinery is targeted to and retained at the hyphal tip.

Summary

Some bacterial proteins operate on the outside of the cell, for example the toxins produced by bacterial pathogens. Since all proteins are made inside the bacterium the extracellular proteins must be moved out of the cell across the normally impermeable cell membrane. This task is carried out by machines termed protein transporters that are located in the cell membrane. One type of transporter moves unfolded proteins, threading them across the membrane like string through the eye of a needle. By contrast, a second type of transporter, which we term the Tat system, moves folded proteins across the membrane. We want to study the Tat transporter in a bacterium called Streptomyces coelicolor. S. coelicolor is an organism that lives in the soil. It lives on dead plant and animal material and to break this material down it needs to export lots of proteins through the Tat transporter. S. coelicolor has a complex lifecycle because it germinates from a spore which grows into structures called hyphae. These hyphae can be thought of as long tubes, and we have shown that the Tat transporter is located at the very tip of these tubes. We have shown this by adding a label to one of the proteins involved in the Tat pathway which makes it appear as coloured spot when viewed in a special type of microscope. In this project we want to understand why and how the Tat transporter is located here. Some of the experiments we will do will find out whether other transporters are also located at the tips of these hyphae by labeling them in a similar way. We want to find mutants of S. coelicolor where the Tat transporter is no longer located in its normal place. We can use these mutants to give us information about the processes that help to locate the Tat transporter at the correct place in the cell.

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Microbiology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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