PBP2B PARTICIPATES IN THE CONTROL OF SHAPE DETERMINATION AND CELL DIVISION MECHANISMS IN STREPTOCOCCUS PNEUMONIAE

A.G. ALBARRACIN ORIO; G.E. PIÑAS; P.R. CORTES; M.B. CIAN; J. ECHENIQUE

Foz de Iguazú

Simposio; The 8th International Symposium on Pneumococci and Pneumococcal Diseases; 2012

Background: Mutations in penicillin-binding proteins (PBPs) PBP1a, PBP2x, and PBP2b confer β-lactam resistance in S. pneumoniae. These enzymes are normally involved in cell wall synthesis. We described that a laboratory strain harboring pbp2b mutations, isolated from clinical strains and that conferred penicillin resistance, showed morphological abnormalities (rod-shaped cells) with an abnormal septum pattern, suggesting alterations in the cell division mechanism. These cell alterations were restored by the acquisition of pbp2x and pbp1a resistance-conferring mutations obtained from clinical strains, showing evidences of a compensatory evolution mechanism. Aims: To analyze the cause by which the PBP2b mutant proteins altered the control of shape determination and its putative involvement in the cell division mechanism. Methods/results: Analyzing PBP-tag protein fusions, we demonstrated that all these pbp mutations conferred an increased stability to their respective mutant proteins, suggesting that a higher half-life of PBP2x and PBP1a mutant proteins is necessary to compensate the increased half-life of the PBP2b mutant protein (PBP2b*) to restore a normal shape. In the pbp2b mutants, we demonstrated that the FtsZ and PBP2B* were delocalized, and that PBP2b* displayed a helix manner, similar to that showed by FtsZ in the same pbp2b mutants. By two-hybrid system assays, we detected a protein-protein interaction between FtsZ and PBP2b*. In addition, we found that PBP2b is able to interact with other proteins that belong to the streptococcal divisome. Conclusions: We proposed that PBP2b participates in the control of shape determination and cell division mechanisms in S. pneumoniae by a direct interaction with FtsZ.