Genetic organization of the she pathogenicity island in Shigella flexneri 2a

Abstract

In this study we report the complete nucleotide sequence and genetic organization of the she pathogenicity island (PAI) of Shigella flexneri 2a strain YSH6000T. The 46 603 bp she PAI is situated adjacent to the 3' terminus of the pheV tRNA gene and includes an imperfect direct repeat of the 3'-terminal 22 bp of the pheV gene at the right boundary of the PAI. The she PAI carries a bacteriophage P4-like integrase gene within the pheV -proximal boundary of the PAI, intact and truncated mobile genetic elements, plasmid-related sequences, open reading frames exhibiting high sequence similarity to those found on the locus of enterocyte effacement (LEE) PAI of enterohemorrhagic Escherichia coli (EHEC), and the SHI-2 PAI of S. flexneri and several other open reading frames of unknown function. The she PAI also encodes two autotransporter proteins, including SigA, a cytopathic protease that contributes to intestinal fluid accumulation and Pic, a protease with mucinase, and hemagglutinin activities. In addition, an open reading frame (orf) termed sap, has high sequence similarity to the gene encoding Antigen 43, a surface-located autotransporter protein of E. coli. The ShET1 enterotoxin genes, associated predominantly with S. flexneri 2a strains, are also located on the she PAI.