A Specific A/T Polymorphism in Western Tyrosine Phosphorylation B-Motifs Regulates Helicobacter pylori CagA Epithelial Cell Interactions
Figure 2
Sequence comparison of the three TPM sites in CagA proteins from different clinical H. pylori strains and specific detection of phosphorylated EPIYT-motif during co-culture.
Panel A: CagA proteins of H. pylori vary in their carboxy-terminal TPM sites. These EPIYA-repeats serve as tyrosine phosphorylation sites of CagA and can be targeted by c-Abl and c-Src kinases. Three EPIYA- or EPIYT-segments at position A, B and C are shaded with yellow. One striking feature of B-TPM is the presence of a threonine residue in the +1 position (shaded with blue) relative to the phosphorylated tyrosine residue, which is highly conserved in most but not all H. pylori strains and may affect the capabilities of binding the p85 subunit of PI3-kinase, as discussed in the text. The CagA protein sequences were obtained from databases and sequence alignment was done using the ClustalW2 program (http://www.ebi.ac.uk/Tools/msa/clustalw2/). Panel B: To investigate whether the EPIYT-motif can be phosphorylated during co-culture, AGS cells were co-incubated with the indicated CagA-expressing H. pylori strains for 6 h. Phosphorylation of CagA was examined using the phospho-specific α-pCagA-EPIYT-918 antibody. Loading of equal amounts of protein in each sample was confirmed by probing with monoclonal α-CagA and α-GAPDH antibodies.