2xi9

Publication Abstract from PubMed

Many bacterial pathogens present adhesins at the tips of long macromolecular filaments known as pili that are often important virulence determinants. Very little is known about how pili presented by Gram positive pathogens mediate host cell binding. The crystal structure of a pilus adhesin from the important human pathogen Streptococcus pyogenes reveals an internal thioester bond formed between the side chains of a cysteine and a glutamine residue. The presence of the thioester was verified using UV-vis spectroscopy and mass spectrometry. This unusual bond has only previously been observed in thioester domains of complement and complement-like proteins, where it is used to form covalent attachment to target molecules. The structure also reveals two intramolecular isopeptide bonds, one of these formed through a Lys/Asp residue pair, that are strategically positioned to confer protein stability. Removal of the internal thioester by allele-replacement mutagenesis in S. pyogenes severely compromises bacterial adhesion to model host cells. Whilst current paradigms of bacterial/host cell interaction envisage strong non-covalent interactions, the present study suggests cell adhesion could also involve covalent bonds.

A highly unusual thioester bond in a pilus adhesin is required for efficient host cell interaction.,Pointon JA, Smith WD, Saalbach G, Crow A, Kehoe MA, Banfield MJ J Biol Chem. 2010 Aug 19. PMID:20729215^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.