Structural highlights
Publication Abstract from PubMedThree pathogenic species of the genus Yersinia assemble adhesive fimbriae via the FGL-chaperone/usher pathway. Closely related Y. pestis and Y. pseudotuberculosis elaborate the pH6 antigen (Psa), which mediates bacterial attachment to alveolar cells of the lung. Y. enterocolitica, instead, assembles the homologous fimbriae Myf of unknown function. Here, we discovered that Myf, like Psa, specifically recognizes beta1-3- or beta1-4-linked galactose in glycosphingolipids, but completely lacks affinity for phosphatidylcholine, the main receptor for Psa in alveolar cells. The crystal structure of a subunit of Psa (PsaA) complexed with choline together with mutagenesis experiments revealed that PsaA has four phosphatidylcholine binding pockets that enable super-high-avidity binding of Psa-fibers to cell membranes. The pockets are arranged as six tyrosine residues, which are all missing in the MyfA subunit of Myf. On the other hand, the crystal structure of the MyfA-galactose complex revealed that the galactose-binding site is more extended in MyfA, enabling tighter binding to lactosyl moieties. Our results suggest that during evolution, Psa has acquired a tyrosine-rich surface that enables it to bind to phosphatidylcholine and mediate adhesion of Y. pestis/pseudotuberculosis to alveolar cells, whereas Myf has specialized as a carbohydrate-binding adhesin, facilitating the attachment of Y. enterocolitica to intestinal cells. This article is protected by copyright. All rights reserved. Structural basis for Myf and Psa fimbriae-mediated tropism of pathogenic strains of Yersinia for host tissues.,Pakharukova N, Roy S, Tuittila M, Rahman MM, Paavilainen S, Ingars AK, Skaldin M, Lamminmaki U, Hard T, Teneberg S, Zavialov AV Mol Microbiol. 2016 Aug 10. doi: 10.1111/mmi.13481. PMID:27507539[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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