title: Molecular genetics, biochemistry and biological role of Yersinia lipopolysaccharide.
abstract: Lipopolysaccharide (LPS) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria. The LPS molecule is composed of two biosynthetic entities: the lipid A--core and the O-polysaccharide (O-antigen). Most biological effects of LPS are due to the lipid A part, however, there is an increasing body of evidence also with Yersinia indicating that O-antigen plays an important role in effective colonization of host tissues, resistance to complement-mediated killing and in the resistance to cationic antimicrobial peptides that are key elements of the innate immune system. The biosynthesis of O-antigen requires numerous enzymatic activities and includes the biosynthesis of individual NDP-activated precursor sugars in the cytoplasm, linkage and sugar-specific transferases, O-unit flippase, O-antigen polymerase and O-chain length determinant. Based on this enzymatic mode of O-antigen biosynthesis LPS isolated from bacteria is a heterologous population of molecules; some do not carry any O-antigen while others that do have variation in the O-antigen chain lengths. The genes required for the O-antigen biosynthesis are located in O-antigen gene clusters that in genus Yersinia is located between the hemH and gsk genes. Temperature regulates the O-antigen expression in Y. enterocolitica and Y. pseudotuberculosis; bacteria grown at room temperature (RT, 22-25 degrees C) produce in abundance O-antigen while only trace amounts are present in bacteria grown at 37 degrees C. Even though the amount of O-antigen is known to fluctuate under different growth conditions in many bacteria very little detailed information is available on the control of the O-antigen biosynthetic machinery.
authors.affiliation: Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Finland.
authors.forename: Mikael
authors.initials: M
authors.lastname: Skurnik
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D019143:Evolution, Molecular; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D019081:O Antigens / Q000235:genetics* / Q000378:metabolism; D009844:Oligosaccharides / Q000737:chemistry; D012703:Serotyping; D014774:Virulence / Q000235:genetics; D015007:Yersinia / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity
chemical_list: D008070:Lipopolysaccharides; D019081:O Antigens; D009844:Oligosaccharides