Structural highlights
FunctionPublication Abstract from PubMedThe human pathogen Streptococcus pyogenes produces pili that are essential for adhesion to host surface receptors. Cpa, the adhesin at the pilus tip, was recently shown to have a thioester-containing domain. The thioester bond is believed to be important in adhesion, implying a mechanism of covalent attachment analogous to that used by human complement factors. Here, we characterize a second active thioester-containing domain on Cpa, termed CpaN. Expression of CpaN in E. coli gave covalently-linked dimers. These were shown by X-ray crystallography and mass spectrometry to comprise two CpaN molecules crosslinked by the polyamine spermidine, following reaction with the thioester bonds. This cross-linked CpaN dimer provides a model for the covalent attachment of Cpa to target receptors and thus the streptococcal pilus to host cells. Similar thioester domains were identified in cell-wall proteins of other Gram-positive pathogens, suggesting that thioester domains are more widely used and provide a mechanism of adhesion, by covalent bonding to target molecules on host cells, that mimics that used by the human complement system to eliminate pathogens. Structural model for the covalent adhesion of the Streptococcus pyogenes pilus through a thioester bond.,Linke-Winnebeck C, Paterson NG, Young PG, Middleditch MJ, Greenwood DR, Witte G, Baker EN J Biol Chem. 2013 Nov 12. PMID:24220033[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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