The accessory Sec system (SecY2A2) in Streptococcus pneumoniae is involved in export of pneumolysin toxin, adhesion and biofilm formation.

ABSTRACT: In Streptococcus pneumoniae TIGR4, genes encoding a SecY2A2 accessory Sec system are present within a locus encoding a serine-rich repeat surface protein PsrP. Mutant strains deleted in secA2 or psrP were deficient in biofilm formation, while the ?secA2 mutant was reduced in binding to airway epithelial cells. Cell wall protein (CWP) fractions from the ?secA2 mutant, but not from the ?psrP mutant, were reduced in haemolytic (pneumolysin) activity. Contact-dependent pneumolysin (Ply) activity of wild type TIGR4 cells was ten-fold greater than that of ?secA2 mutant cells suggesting that Ply was not active at the ?secA2 cell surface. Ply protein was found to be present in the CWP fraction from the ?secA2 mutant, but showed aberrant electrophoretic migration indicative of protein modification. Proteomic analyses led to the discovery that the ?secA2 mutant CWP fraction was deficient in two glycosidases as well as other enzymes involved in carbohydrate metabolism. Taken collectively the results suggest that positioning of Ply into the cell wall compartment in active form, together with glycosyl hydrolases and adhesins, requires a functional accessory Sec system.

SUBMITTER: Bandara M 

PROVIDER: S-EPMC5526788 | biostudies-literature | 2017 Jul - Aug

REPOSITORIES: biostudies-literature