Fig. 4

Alignment of EPIYA-motif sequences in CagA proteins derived from seven geographically different H. pylori strains. All chosen strains carry the typical East Asian CagA protein with the carboxy-terminal EPIYA-A, EPIYA-B and EPIYA-D phosphorylation sites. Host kinases such as c-Src and c-Abl were shown to target and phosphorylate the tyrosine residue in these motifs. The specific EPIYA-segments A, B and D are indicated with yellow shading and exhibit variations in their flanking regions depending on their geographical origins. A special attribute is present in the EPIYA-B motif by the presence of a negatively charged glutamate residue in the -4 position (shaded with green). This residue is highly conserved in EPIYA-B among the different H. pylori strains and might lead to alterations of the binding capacity of phosphotyrosine antibodies as discussed in the text. The CagA protein sequences were obtained either from databases or sequenced during this study (Table 1). Sequence alignment was done using the ClustalW2 program (http://www.ebi.ac.uk/Tools/msa/clustalw2/)