title: Localisation of Helicobacter pylori catalase in both the periplasm and cytoplasm, and its dependence on the twin-arginine target protein, KapA, for activity.
abstract: Helicobacter pylori induces a severe inflammatory response in the gastric mucosa. It is able to withstand the inflammatory response by producing proteins such as KatA and KapA. The C-terminus of KatA possesses a unique tetra-lysine motif not found in other catalases or other known protein sequences. Mutants deficient in this motif were constructed by site-directed mutagenesis. Cytoplasmic and periplasmic catalase activities were measured for the parental strain, a truncated KatA mutant (deficient in the unique C-terminal tetra-lysine motif) and a previously constructed KapA-deficient mutant (confirming previous observations regarding the possible periplasmic localisation of KatA). No differences were observed in the cytoplasmic catalase activities, however, the KapA-deficient mutant had approximately 5.5 times less catalase activity in the periplasmic extract when compared to the periplasmic preparations of either parental strain or KatA truncated mutant. N-terminal sequencing of KatA revealed no cleaved N-terminal signal peptide, indicating Sec-independent transport. These findings support previous reports that there is some form of interaction between KatA and KapA of H. pylori, an interaction which still needs to be characterised.
authors.affiliation: MRC Molecular Pathogenesis group, Centre for Infectious Diseases, Institute for Cell and Molecular Sciences, Queen Mary College, University of London, Whitechapel, London E1 2AA, UK. a.g.harris@qmul.ac.uk
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Harris
authors.forename: Stuart L
authors.initials: SL
authors.lastname: Hazell
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002374:Catalase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology; D016480:Helicobacter pylori / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018384:Oxidative Stress; D019897:Periplasm / Q000201:enzymology; D017433:Protein Structure, Secondary
chemical_list: D001426:Bacterial Proteins; D001120:Arginine; D002374:Catalase