Protein cleavage generates functional diversity on the surface of bacterial pathogens

Protein cleavage generates functional diversity on the surface of bacterial pathogens

Protein cleavage generates functional diversity on the surface of bacterial pathogens (#34)

Steven P Djordjevic ¹

University of Technology, Sydney, Broadway, NSW, Australia

Bacterial pathogens are known to post-translationally cleave large mass, surface molecules during maturation but the extent to which processing occurs on the cell surface has largely remained unexplored. We have been characterising post-translational cleavage events in cell surface proteins produced by several pathogenic mycoplasma species. Cell shaving and cell surface biotinylation protocols in combination with LC-MS/MS and 2D-PAGE have been used to generate comprehensive datasets that identify the complement of cell surface proteins and predict cleavage sites, such as the now well-characterised S/T-X-F↓X-D/E motif found in the P97 and P102 adhesin families (1-7). Our complementary, orthogonal approaches show that adhesins, lipoproteins, non-classically secreted proteins, and proteins predicted by PSORTb to localise to the cytosol can be cleaved. To investigate the functional significance of protein processing, we have developed a series of affinity-capture protocols using heparin, fibronectin, plasminogen, actin and host epithelial cell surface antigens as bait (1-7). Cleavage fragments representing different regions of the same molecule have been shown to bind to different extracellular matrix components and host surface-associated molecules (1-7). Independent studies show that these interactions occur with physiologically relevant binding affinities suggesting that processing may be a mechanism to increase the repertoire of functionally diverse proteins on the cell surface of these genome-reduced pathogens.

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Authors contributing to this presentation.

Djordjevic, S.P

Professor Steven Djordjevic leads the Pathogen Proteomics and Genomics group located at the ithree (infection, immunology and innovation) institute, University of Technology Sydney (UTS). He is a member of the governing board and the scientific manage committee for the Australian Centre for Genomic Epidemiological Microbiology (AusGEM). He is director of the Proteomics Core Facility for the Faculty of Science at UTS. Steven Djordjevic has over 25 years experience in bacterial pathogenesis and molecular epidemiology. He has made substantial contributions to these fields. Djordjevic has led development of implemented molecular diagnostic tests for major veterinary and zoonotic pathogens. More recently, to inform vaccine development, his team has identified and functionally analysed proteins on the surface of bacterial cells using systems biology approaches. His team has shown that post-translational processing of surface proteins on Mycoplasmas is critical for interaction of the bacteria with the mammalian host. He is a proponent of the ‘One Health’ approach to surveillance of antibiotic resistance. He works closely with industry, clinical microbiologists, clinicians, veterinarians and microbial ecologists to gain a comprehensive picture of how antibiotic resistance and virulence genes are transferred from reservoirs of infection. Together they are developing and implementing novel diagnostic assays to enhance surveillance activities. They characterise mobile elements such as transposons, plasmids, genomic islands that are central to capture and spread of antimicrobial resistance genes, and decipher the molecular phylogeny of Gram negative bacteria that harbour these mobile genetic elements. Their studies give insight into underlying epidemiology and aim to better inform policy and practice. Djordjevic was awarded a PhD in Biochemistry and Molecular Biology from the Australian National University in 1988. Post-PhD he was employed by the NSW Department of Primary Industries at the Elizabeth Macarthur Agricultural Institute. In 2009 he accepted an academic appointment at the University of Technology Sydney.

Protein cleavage generates functional diversity on the surface of bacterial pathogens (#34)

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