FIG. 1.

A+T content and genetic organization of the sit locus encoded in the centisome 63 pathogenicity island of S. typhimurium. The region between orgA and fhlA was cloned by chromosomal walking, resulting in the plasmid pSB857. The nucleotide sequence of the region located immediately downstream of fhlA was determined. Four ORFs (sitA, sitB, sitC, and sitD) apparently arranged in a single transcriptional unit were identified. Abbreviations for restriction enzymes: E, EcoRI; EV, EcoRV; N, NdeII; H, HpaI. An asterisk indicates that the restriction site has been destroyed by cloning.