The conserved domains and homology analysis of VCA0518 encoding product of the toxigenic strain N16961, nontoxigenic strains JS32 and 60–61. The thick line on the top of the figure means the whole length of the predict peptide chain of the VCA0518 product. The conserved domains are marked with the grey rectangles under the line. Fourteen mutated residues distributed at six sites from amino acids 200 to 310 are shown below the domain map. Residue changes are listed on the bottom of the figure. Amino acid residues with polarity or acid-alkaline changes are marked with *.