Structure, function and biology of proteases and protease inhibitors
We have a long-standing interest in proteolysis. Current projects include a focus around fibrinolysis, the mechanism through which the body removes blood clots and repairs damaged tissue following injury or infection (see Law et al., 2012, Cell Reports). Specifically, we are studying how the plasminogen / plasmin system is activated, how this protease binds target receptors, substrates and inhibitors, and how bacterial virulence factors hijack the plasminogen system to enhance invasiveness. Furthermore, together with Prof Rob Pike, we are studying the proteases of the complement system, an ancient immune defence system that is commonly deregulated in a range of different inflammatory diseases.
In a separate research direction, together with Prof Phil Bird, we are studying the biology of maspin, a tumour suppressor in breast and other cancers (see Law et al., 2005 JBC). Maspin is a member of the serine protease inhibitor (serpin) superfamily, however, it is postulated to have lost its ability to inhibit target proteases. Accordingly, the molecular targets in normal and cancerous tissue remain unclear.
Investigating the conjugation machinery of Gram positive pathogens
Together with Prof Julian Rood our team is investigating the machinery that allows Gram positive organisms, and particularly Clostridial species to exchange DNA. Bacterial conjugation is essential to the acquisition of virulence and antibiotic resistance genes and the evolution of "superbugs" that are resistant to most commonly available antibiotics. Using a combination of structural biology, biochemistry and microbial genomics we are starting to elucidate the molecular mechanism through which DNA exchange between Gram positive bacteria is achieved (see Porter et al., Mol Micro, 2011)
Membrane attack complex / perforin-like proteins (MACPF) in immunity and developmental biology
Members of the MACPF superfamily are pore-forming proteins that play key roles in the human immune response. The membrane attack complex (MAC) itself functions in the latter stages of the complement pathway to destroy foreign cells and bacteria whereas perforin is secreted by Cytotoxic T-lymphocytes and Natural Killer Cells in order to destroy virally infected and malignant cells. We determined the first structure of a MACPF protein (Rosado et al., 2007, Science) and showed that these molecules are distantly related to an important family of bacterial virulence factors - the cholesterol dependent cytolysins. In a second paper, in collaboration with Prof Joe Trapani (Peter Mac) and Prof Helen Saibil (Birkbeck College, London), we determined the structure of perforin and related these data to a cryo-EM structure of the perforin pore (Law et al., Nature, 2010). We are now interested in understanding how perforin-like proteins recognise membranes, and the molecular details of the perforin pore. In addition, we are part of a Wellcome Trust funded research program to develop perforin inhibitors (led by the Peter Mac and together with the University of Auckland and the University of Queensland) (http://www.wellcome.ac.uk/Funding/Technology-transfer/Funded-projects/Therapeutics/index.htm). These molecules are anticipated to be of utility in improving the success rates of allergenic bone marrow transplantation for the treatment of cancer.
Most MACPF proteins characterised to date are lytic (pore forming) molecules that function in immunity and defence. However, a wide range of MACPF proteins appear to play essential roles in developmental biology and neurobiology. It is currently unknown whether this branch of the MACPF superfamily retains the ability to form pores or indeed whether these proteins interact with membranes. To study the role and molecular function of these molecules we are using three primary model systems - Drosophila (in collaboration with A/Prof Coral Warr), Zebra fish (with Dr Heather Verkade and Prof Phil Bird) and the mouse (with Prof Phil Bird).