Tyrosine Phosphorylation of the Bacterial Stress Factor BipA aids in Adaptation and Pathogenicity

Summer 2016

Investigators: Akua Owusu and Jui Chaugule

Faculty Advisors: Dr Victoria Robinson and Dr David Benson

BipA is a multi-domain prokaryotic GTPase universally conserved in pathogenic bacteria.  It regulates a number of virulence events including pedestal formation, flagella mediated motility and expression of virulence genes. Most importantly, BipA null mutants are avirulent, suggesting it is a prime target for antimicrobial development.  Central to the function of BipA are its GTPase activity and its association with the ribosome. An examination of the ribosome binding properties of the protein revealed that BipA has two ribosome binding modes. Under normal growth conditions, GTP-bound BipA associates with 70S ribosomes. However, under conditions of stress, ppGpp-bound BipA associates with 30S ribosomes. A study by the O’Connor group at the University of Southampton (UK) demonstrated that BipA undergoes phosphorylation on one of its tyrosine residues and perhaps this modification may play a role in its ability to regulate virulence processes. Therefore, the purpose of my project was to identify the tyrosine phosphorylation sites in EHEC BipA and then determine how this modification affects its biochemical properties particularly its GTPase activity.