Defining the cytoplasmic architecture that control bacterial type three secretion

Many pathogenic bacteria use nano-machines to inject proteins into their hosts' cells to promote infection and colonisation by the bacterium. One such machine is called the Type Three Secretion System or T3SS. This application seeks to investigate the way in which bacteria select and secrete proteins by using a combination of different structural and functional methods. In particular we will study two pieces of the machine that are assembled within the bacterium which genetic evidence suggests are important for the process of selecting which proteins should be injected into the host and are also implicated in the actual process of driving injection. By using methods which allow us to "see" how these parts of the machine are constructed and complementing this with studies where we make small changes in the components from which the machines are constructed and look to see what effect this has on the function of the machinery we hope to deduce the molecular mechanisms of control. Since this machinery is only found in bacteria there is the potential that a good understanding of the T3SS will eventually lead to new antibiotics which are designed to specifically interfere with this key activity.

Many pathogenic bacteria use nano-machines to inject proteins into their hosts' cells to promote infection and colonisation by the bacterium. One such machine is called the Type Three Secretion System or T3SS. This application seeks to investigate the way in which bacteria select and secrete proteins by using a combination of different structural and functional methods. In particular we will study two protein complexes known as the Export Apparatus (EA) and the C-ring that are assembled within the bacterium which genetic evidence suggests are important for the process of selecting which proteins should be injected into the host and are also implicated in the actual process of driving injection.
By using structural and biochemical methods to define how these parts of the machine are constructed and complementing this with in vivo studies of structurally-informed mutations within the components from which the machines are constructed we hope to deduce the molecular mechanisms of control of secretion. Since this machinery is only found in bacteria there is the potential that a good understanding of the T3SS will eventually lead to new antibiotics which are designed to specifically interfere with this key pathogenic activity.

In addition to the high probability of novel findings and hence strong academic impact on the understanding of both secretion and movement related type three systems (e.g. the Wellcome Trust Programme that has funded the work over the last 5 years has led to more than five papers that have already been cited more than 25 times and two papers cited more than 50 times) there is also potential for impact in terms of design of novel antibacterial agents. Since type three secretion systems are critical for bacterial virulence (both the secretion and movement associated ones) and since they are systems not found in mammalian hosts they are obvious therapeutic targets. To date there are no licensed therapeutics targeting this assembly and this probably reflects our relatively poor understanding of the mechanisms of control of secretion. The work proposed in this application will significantly increase our understanding of the control systems and, in particular by furnishing atomic structures for components, lead itself to suggesting avenues for further exploitation for drug discovery. Both the applicants are involved in other projects where basic science has informed potential therapeutics and are actively working with industrial partners to develop these ideas (both Novartis and Pfizer) - we will therefore ensure that any potential for such development is rapidly exploited in an efficient fashion.