Localisation of Helicobacter pylori catalase in both the periplasm and cytoplasm, and its dependence on the twin-arginine target protein, KapA, for activity.
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.
Harris
Andrew G
AG
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
Hazell
Stuart L
SL
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
D001426:Bacterial Proteins; D001120:Arginine; D002374:Catalase