부산대학교 도서관

The lipopolysaccharide of certain strains ofHelicobacter pyloriwas recently shown to contain the Lewis X (Lex) trisaccharide (Galβ-1,4-(Fucα(1,3))-GlcNAc). Lexis an oncofetal antigen which appears on human gastric epithelium, and its mimicry by carbohydrate structures on the surface of H. pylorimay play an important part in the interaction of this pathogen with its host. Potential roles for bacterial Lexin mucosal adhesion, immune evasion, and autoantibody induction have been proposed (Moran, A. P., Prendergast, M. M., and Appelmelk, B. J. (1996) FEMS Immunol. Med. Microbiol.16, 105–115). In mammals, the final step of Lexbiosynthesis is the α(1,3)-fucosylation of GlcNAc in a terminal Galβ(1→4)GlcNAc unit, and a corresponding GDP-fucose:N-acetylglucosaminyl α(1,3) fucosyltransferase (α(1,3)-Fuc-T) activity was recently discovered in H. pyloriextracts. We used part of a human α(1,3)-Fuc-T amino acid sequence to search an H. pylorigenomic data base for related sequences. Using a probe based upon weakly matching data base sequences, we retrieved clones from a plasmid library of H. pyloriDNA. DNA sequence analysis of the library clones revealed a gene which we have named fucT, encoding a protein with localized homology to the human α(1,3)-Fuc-Ts. We have demonstrated that fucT encodes an active Fuc-T enzyme by expressing the gene in Escherichia coli. The recombinant enzyme shows a strong preference for type 2 (e.g.LacNAc) over type 1 (e.g.lacto-N-biose) acceptors in vitro.Certain residues in a short segment of the H. pyloriprotein are completely conserved throughout the α(1,3)-Fuc-T family, defining an α(1,3)-Fuc-T motif which may be of use in identifying new fucosyltransferase genes.