A C-terminal translocation signal is necessary, but not sufficient for type IV secretion of the

Helicobacter pylori CagA protein

Molecular Microbiology 59 (5): 1624- 1637, 2006

Speaker : 莊旭翔                                                                  Time : 3/1/2006, 15:00-16:00

Commentator : 呂政展老師                                          Place : Room 601

Abstract :

Type IV secretion systems were increasingly recognized as important pathogenicity determinants. One of examples was Cag secretion system of H. pylori. In this apparatus, CagA protein was translocated into gastric epithelial cell and tyrosine-phosphorylated by Src family kinases. Subsequent influences were induction of cell scattering, or an interference with the integrity of tight junction complexes. In our knowledge, many populations, infection with cag PAI H. pylori strains has been associated with increased risk of severe gastritis , peptic ulceration, atrophic gastritis , and distal gastric cancer of the intestinal type. In this paper, authors found that CagA translocation depends on the presence of its 20 C- terminal amino acids , containing an array of positively charged residues. Surprisingly, these positively charges weren’t necessary for CagA translocation. Authors used a phosphorylatable peptide tag for CagA type IV translocation assay. They found that removal of the N-terminal residues of CagA protein results in translocation- incompetent of CagA protein. These results indicated that both C-terminal and N-terminal residues of CagA protein are necessary for its translocation.

References:

1. Sabine, Hohlfeld. et al. A C-terminal translocation signal is necessary, but not sufficient for type IV secretion of the Helicobacter pylori CagA protein. Mol. Microbiol. 5, 1624-1637 (2006).

2. Cascales, E., and Christie, P.J. The versatile bacterial type IV secretion systems. Nat Rev Microbiol 1: 137– 149 (2003).