Assembly of pili in Gram-positive bacteria

Amide bonds assemble pili on the surface of bacilli

“…We surmise that, apart from incorporating peptidase resistance, intramolecular amide bonds may be important for precursor folding and presentation of the YPKN nucleophile to SrtD intermediates. Conservation of sortase catalysts and pilin proteins with the YPKN motif, the LPXTG sorting signal, and the CNA B domains suggests that the mechanism of pilus assembly is universal in Gram-positive bacteria (26). These insights may aid in the design of pilus-derived vaccines to prevent diseases caused by Gram-positive bacteria (27).…”

Structure of the Bacillus anthracis Sortase A Enzyme Bound to Its Sorting Signal

“…Transglycosylation and transpeptidation reactions that synthesize the cell wall then incorporate this product into the peptidoglycan. Other members of the sortase superfamily are believed to operate through a similar enzymatic mechanism as Sa SrtA, but in some microbes (primarily enterococal and corynebacterial species), sortases perform equivalent transpeptidation reactions that assemble pili on the bacterial cell surface (16).…”

Functional Identification of Conserved Residues Involved in Lactobacillus rhamnosus Strain GG Sortase Specificity and Pilus Biogenesis

“…Various other Gram-positive bacteria displaying pili were subsequently described, such as Actinomyces, Clostridia, or Enterococci (2,3). Until recently, it was acknowledged that pili were a phenotypic trait characteristic to pathogenic bacteria.…”

“…Typically, pilin precursors harbor a N-terminal peptide signal that allow secretion of the pilin subunits through the Sec-dependent secretion pathway (2). Following secretion and cleavage of its N-terminal peptide signal, the pilin subunit is retained to the cell membrane by its C-terminal hydrophobic domain (3). They are then covalently coupled to each other by isopeptide bonds that are catalyzed by pilin-specific sortases (12,14,16).…”