MOLECULAR CHARACTERIZATION OF THE OAFA LOCUS RESPONSIBLE FOR ACETYLATION OF SALMONELLA-TYPHIMURIUM O-ANTIGEN - OAFA IS A MEMBER OF A FAMILYOF INTEGRAL MEMBRANE TRANS-ACYLASES

Lipopolysaccharide (LPS) coats the surface of gram-negative bacteria a nd serves to protect the cell from its environment, The O-antigen is t he outermost part of LPS and is highly variable among gram-negative ba cteria, Strains of Salmonella are partly distinguished by serotypic di fferences in their O-antigen. In Salmonella typhimurium, the O-antigen is acetylated, conferring the O5 serotype, We have previously provide d evidence that this modification significantly alters the structure o f the O-antigen and creates or destroys a series of conformational epi topes, Here we report the detailed mapping, cloning, and DNA sequence of the oafA gene, The locus contains one opera reading frame that is p redicted to encode an inner membrane protein, consistent with its role in modification of the O-antigen subunit, The OafA protein shows homo logy to proteins in a number of prokaryotic and one eukaryotic species , and this defines a family of membrane proteins involved in the acyla tion of exported carbohydrate moieties, In many of these instances, ac ylation defines serotype or host range and thus has a profound effect on microbe-host interaction.