Fig. 7

Selection for sequence diversification in inhibitory receptor Ceacams. The accumulation of non-synonymous (green curves) and synonymous substitutions (red curves) along the N exons of orthologous (a-c) and homeologous inhibitory receptor gene pairs (d) were determined after manual removal of gaps in the compared nucleotide sequences. The names of the analyzed genes are indicated in the top left corner of the graph. Note the rapid accumulation of nonsynonymous mutations in the CC’C”FG β-strand regions (black broken lines) which indicates selection for diversification. This contrasts with conserved regions between CC’C” and FG β-strands indicated by red broken lines. The location of CC’C” and FG β-strand regions determined by 3D modeling (Additional file 4) are indicated by gray boxes above the graphs. Note the sequence identity of the 38 N terminal codons in the N exon of X. laevis homeologs ceacam389.L and ceacam389.S possibly caused by interchromosomal recombination. N, N domain exon; Xla, X. laevis; Xtr, X. tropicalis