Matthew Jorgenson will present his research on 18th October 2012
TOWARD DETERMINING THE FUNCTION OF RLPA, A CELL DIVISION PROTEIN FROM PSEUDOMONAS AERUGINOSA
Cell division is an essential process, requiring the concerted efforts of at least 30 proteins in a Gram-negative bacterium like Escherichia coli. Together, these proteins form a complex structure at the midcell known as the septal ring to mediate the simultaneous inward growth of the three layers of the cell envelope: the outer membrane, the peptidoglycan cell wall, and the inner membrane. Recently, our lab identified three new septal ring proteins—DamX, DedD and RlpA—in E. coli, all of which contain a ~75 amino acid SPOR domain that is sufficient for localization to the septal ring. Loss of DamX or DedD resulted in cell division defects. Conversely, loss of rare lipoprotein A (RlpA) did not cause a cell division defect in E. coli. However, we found that a transposon mutant of rlpA in Pseudomonas aeruginosa has defects in cell separation when grown in mediaof low ionic strength, forming chains of 4-8 cells. We constructed a non-polar deletion of rlpA in P. aeruginosa and confirmed the chaining phenotype. We also constructed an RlpA-mCherry fusion and showed septal ring localization during cell division. Interestingly, the SPOR domain is necessary for RlpA localization but not for function. Utilizing the RlpA-mCherry fusion, we also show that RlpA is an outer membrane lipoprotein. Peptidoglycan analysis revealed some structural differences between wild type and the rlpA mutant, suggesting RlpA is an enzyme involved in peptidoglycan turnover or maturation. Data from an in vitro assay combining purified RlpA with isolated peptidoglycan supports this hypothesis.