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.