Figure 4. Alignment of A17 regions from different strains displaying putative "deleted" regions involving different number of repeated sequence elements.
A. The repeats present in the longest A17 sequence were arbitrarily defined according to the compared sequences and are as follows: FK = FKNGKNKDFSKVTQAKSDLENS, a repeat of 22 amino acids with copies in CagA outside the A17 region; QAVS = tetrapeptide as shown; EPI = a repeated EPIYA polypeptide segment (up to 5 copies) with a sequence variation (EPIYT); FP = FPLKRHDKVDDLSKVGLS, an 18 amino acid repeat; TI = an eight amino acid polypeptide repeat with the sequence TIDDLGGP. N5 is a non-repeated tract of five or six Asn displayed as reference close to the first EPIYA in A17. The drawing is at scale, and the boxes show their approximate positions. No functions have been assigned to these repeated elements, with the exception of the EPIYA, which has been proposed as phosphorylation sites of tyrosine in CagA (Odenbreit et al., 2000).
B. The alignment of nine A17 sequences is represented by lines. Line discontinuities correspond to deleted regions. Sizes (in amino acids) expected for the A17 fragments are indicated at the right.
C. Outline of the longest deleted regions observed in A17 sequences from different H. pylori strains. Boxed numbers indicate the length of the missing sequences (in amino acids) respect to the longest A17 region.