The pH 6 Antigen of Yersinia pestis Binds to β1-Linked Galactosyl Residues in Glycosphingolipids

Abstract

The Yersinia pestis pH 6 antigen was expressed by, and purified from, Escherichia coli containing cloned psa genes. By an enzyme-linked immunosorbence-based assay, purified pH 6 antigen bound to gangliotetraosylceramide (GM1A), gangliotriaosylceramide (GM2A), and lactosylceramide (LC) (designations follow the nomenclature of L. Svennerholm [J. Neurochem. 10:613–623, 1963]). Binding to GM1A, GM2A, and LC was saturable, with 50% maximal binding occurring at 498 ± 4, 390, and 196 ± 3 nM, respectively. Thin-layer chromatography (TLC) overlay binding confirmed that purified pH 6 antigen bound to GM1A, GM2A, and LC and also revealed binding to hydroxylated galactosylceramide. Intact E. coli cells which expressed the pH 6 antigen had a specificity similar to that of purified pH 6 in the TLC overlay assay except that nonhydroxylated galactosylceramide was also bound. The binding patterns observed indicate that the presence of β1-linked galactosyl residues in glycosphingolipids is the minimum determinant required for binding of the pH 6 antigen.

Comparative transcriptomics in Yersinia pestis: a global view of environmental modulation of gene expression

“…pH6 antigen (PsaA), encoded by the chromosomal psaA gene, expresses in vitro between pH 5 and 6.7 at 35 to 41°C [ 28 ], or when bacteria live within phagocytic phagolysome [ 29 ]. The psaEFABC operon encodes a chaperone/usher pathway involved in the secretion and assembly of pH6 antigen as a polymer (fimbriae) on the surface of Y. pestis in macrophages [ 28 , 30 ]. PsaE is thought to be a positive regulator of the psaABC locus and is required for maximal expression of the pH6 antigen [ 31 ].…”

The regulatory roles of glycosphingolipid‐enriched lipid rafts in immune systems

“…Lactosylceramide is expressed not only on neutrophils but also on intestinal epithelial cells, and binds to various microorganisms, such as Mycobacterium avium‐intracellulare complex (MAC), M. tuberculosis , C. albicans , Bacillus dysenteriae , Bordetella pertussis , E. coli , and Propionibacterium freudenreichii . Human and bovine milk contain LacCer as a major GSL component , indicating that milk‐derived LacCer is a putative trap and blocking pathogen binding in the intestines, and that milk‐derived LacCer protects the host from invading pathogens.…”

Yersinia virulence factors - a sophisticated arsenal for combating host defences

“…PsaA possesses a flexible fimbrial structure that is highly expressed during macrophage infection 120 . Biochemical examination of Psa reveals that it binds to β1-linked galactosyl residues in glycosphingolipids 121 , mainly of the type found in apolipoprotein-B-containing lipoproteins in human plasma, such as low-density lipoprotein (LDL) and in lipid rafts in macrophage membranes 122 . Furthermore, Psa acts as a bacterial Fc receptor, binding human immunoglobulin (IgG) but not reacting with rabbit, mouse, or sheep IgG 123 .…”