title: Carboxyl terminus of Helicobacter pylori alpha1,3-fucosyltransferase determines the structure and stability.
abstract: Helicobacter pylori is well known as the primary cause of gastritis, duodenal ulcers, and gastric cancer. The pathogenic bacteria produces Lewis x and Lewis y epitopes in the O-antigens of lipopolysaccharides to mimic the carbohydrate antigens of gastric epithelial cells to avoid detection by the host's immune system. The enzyme alpha1,3-fucosyltransferase from H. pylori catalyzes the glycosyl addition of fucose from the donor GDP-fucose to the acceptor N-acetyllactosamine. The poor solubility of the enzyme was resolved by systematic deletion of the C-terminus. We report here the first structural analysis using CD spectroscopy and analytical ultracentrifugation. The results indicate that up to 80 residues, including the tail rich in hydrophobic and positively charged residues (sequence 434-478) and 5 of the 10 tandem repeats of 7 amino acids each (399-433), can be removed without significant change in structure and catalysis. Half of the heptad repeats are required to maintain both the secondary and native quaternary structures. Removal of more residues in the C-terminus led to major structural alteration, which was correlated with the loss of enzymatic activity. In accordance with the thermal denaturation studies, the results support the idea that a higher number of tandem repeats functioning to facilitate a dimeric structure helps to prevent the protein from unfolding during incubation at higher temperatures.
authors.affiliation: Institute of Biological Chemistry and Genomics Research Center, Academia Sinica, No. 128 Academia Road Section 2, Nan-Kang, Taipei 11529, Taiwan.
authors.forename: Sheng-Wei
authors.initials: SW
authors.lastname: Lin
authors.forename: Tsui-Min
authors.initials: TM
authors.lastname: Yuan
authors.forename: Jei-Ru
authors.initials: JR
authors.lastname: Li
authors.forename: Chun-Hung
authors.initials: CH
authors.lastname: Lin
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D001483:Base Sequence; D002942:Circular Dichroism; D017931:DNA Primers; D004795:Enzyme Stability; D005647:Fucosyltransferases / Q000737:chemistry*; D016480:Helicobacter pylori / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D014461:Ultracentrifugation
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; D005647:Fucosyltransferases; C031692:galactoside 3-fucosyltransferase