Structural basis for group B streptococcus pilus 1 sortases C regulation and specificity.

ABSTRACT: Gram-positive bacteria assemble pili through class C sortase enzymes specialized in polymerizing pilin subunits into covalently linked, high-molecular-weight, elongated structures. Here we report the crystal structures of two class C sortases (SrtC1 and SrtC2) from Group B Streptococcus (GBS) Pilus Island 1. The structures show that both sortases are comprised of two domains: an 8-stranded ?-barrel catalytic core conserved among all sortase family members and a flexible N-terminal region made of two ?-helices followed by a loop, known as the lid, which acts as a pseudo-substrate. In vitro experiments performed with recombinant SrtC enzymes lacking the N-terminal portion demonstrate that this region of the enzyme is dispensable for catalysis but may have key roles in substrate specificity and regulation. Moreover, in vitro FRET-based assays show that the LPXTG motif common to many sortase substrates is not the sole determinant of sortase C specificity during pilin protein recognition.

SUBMITTER: Cozzi R 

PROVIDER: S-EPMC3493515 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature