Probing the mechanism of the Tat protein transport system at the single complex level in whole bacterial cells

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. In this project we want to increase our understanding of how the Tat system works. We have added labels to the various proteins involved in the Tat pathway which make them appear as coloured spots when viewed in a special type of microscope. We can even see the spots in whole bacterial cells. By studying the behaviour of the spots we can learn about how the Tat components function in living cells. The Tat system is a possible drug target because it is required for bacterial pathogenesis but is not found in humans. It is also of biotechnological interest because it could be used to secrete useful protein products.

The Tat protein transport system functions to export folded proteins across the bacterial cytoplasmic membrane. TatA, TatB and TatC are the essential components of the bacterial Tat protein export pathway and interact in a dynamic manner to form the membrane-located protein complexes necessary for substrate transport. We will use strains that express fluorescently-tagged Tat components at wild-type levels in conjunction with advanced imaging techniques to study individual Tat components under physiologically relevant conditions in whole bacterial cells.