FIG. 2.

Primer extension mapping of the transcription start site. RNA was isolated from S. aureus ISP546 (lanes 1 and 3) and KSI2054 (lanes 2 and 4) harboring plasmid pZS2704 (lanes 3 and 4) or pZS2743 (lanes 1 and 2) at an optical density at 540 nm of 1.2. Reverse transcription was carried out using the primer cat3, which anneals to a site near the 5′ end of the cat gene. The samples were loaded into adjacent lanes of a sequencing gel, and the lanes between the two sets were left blank. The sequence ladder was generated using the same primer and pZS2704 as the template. The transcription start site is indicated as +1.