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Lewis (Le) antigens are fucosylated oligosaccharides present in theHelicobacter pylori lipopolysaccharide. Expression of these antigens is believed to be important forH. pylori colonization, since Le antigens also are expressed on the gastric epithelia in humans. A galactosyltransferase encoded by β-(1 ,3 )galT is essential for production of type 1 (Lea and Leb ) antigens. The upstream genejhp0562 , which is present in many but not allH. pylori strains, is homologous to β-(1 ,3 )galT but is of unknown function. BecauseH. pylori demonstrates extensive intragenomic recombination, we hypothesized that these two genes could undergo DNA rearrangement. A PCR screen and subsequent sequence analyses revealed that the two genes can recombine at both the 5′ and 3′ ends. Chimeric β-(1 ,3 )galT -like alleles can restore function in a β-(1 ,3 )galT null mutant, but neither native nor recombinantjhp0562 can. Mutagenesis ofjhp0562 revealed that it is essential for synthesis of both type 1 and type 2 Le antigens. Transcriptional analyses of both loci showed β-(1 ,3 )galT expression in all wild-type (WT) and mutant strains tested, whereasjhp0562 was not expressed injhp0562 null mutants, as expected. Sincejhp0562 unexpectedly displayed functions in both type 1 and type 2 Le synthesis, we asked whethergalT , part of the type 2 synthesis pathway, had analogous functions in type 1 synthesis. Mutagenesis and complementation analysis confirmed thatgalT is essential for Leb production. In total, these results demonstrate thatgalT andjhp0562 have functions that cross the expected Le synthesis pathways and thatjhp0562 provides a substrate for intragenomic recombination to generate diverse Le synthesis enzymes.

Novel Functions for Glycosyltransferases Jhp0562 and GalT in Lewis Antigen Synthesis and Variation in Helicobacter pylori