Sequence analysis of β-hemolysin gene of Aeromonas hydrophila isolated from Anguilla anguilla

The complete β-hemolysin gene of an Aeromonas hydrophila strain ML316 isolated from diseased Anguilla anguilla (named AHL316HEM) had been cloned and sequenced. The structural analysis proved that the AHL316HEM had a 1482bp open reading frame (ORF), encoding a putative peptide with 493 amino acids and 54. 2kD in size, the isoelectric point of the protein was 5. 625. Enzyme restriction site analysis found that there was an EcoRI restriction site within the ORF, meanwhile other reference hemolysin genes been analyzed did not have the same restriction site. Obviously, there was a hydrophobic regions located in the first 23-amino-acid of the peptide, this region might function as a signal peptide, and most of the antigenicity sites were distributed in the hydrophilic regions of the protein, this region did not have penetrability. Amino acid homologous comparioson was conducted between the AHL316HEM and Aeromonas hydrophila hemolysin of BAA83088, Aeromonas punctata hemolysin (accession No. U40711) , Aeromonas sobria hemolysin (accession No. AF443393) , the identity were 98%, 84% and 72% respectively; and the identity between AHL316HEM and the other hemolysin gene of Vibrio cholerae (accession No. AF540655), Vibrio parahaemolyticus (accession No. VIBTRH2A), Staphytococcus aureus (accession No. S72497)were only 7% ,5% ,4% , these results indicated the hemolysin gene of the aeromonas genus bacteria might have same origin.