Table 2.

β-Lactamase activities of the different fusions of thenorA promoter in S. aureusISP794a

PlasmidPromoterFusionβ-Lactamase activityb (U/g)Ratioc
pWN1818None≤2,000
pBF2Wild typeTranslational3,690 ± 2401
pBF1flqBTranslational16,600 ± 1,1304.5
pWN2018None≤2,000
pBF8-30Wild typeTranscriptional10,200 ± 1,7001
pBF5-10Wild type truncated of 5′ mRNATranscriptional3,740 ± 6800.4
pBF15-5Wild type truncated of region upstream of the promoterTranscriptional9,230 ± 5100.9
pBF7-7flqBTranscriptional50,200 ± 4,6104.9
  • a DNA fragments (Fig. 1) were amplified by PCR, cloned into pGEM3-zf(+) (Promega), and then subcloned into theKpnI and PstI sites of pWN1818 or pWN2018 (27). The plasmid inserts were then sequenced, and the plasmids were introduced by electroporation first into S. aureus RN4220 (12) and then into strain ISP794 (24), using selection with chloramphenicol (20 μg/ml). β-Lactamase activity was measured at room temperature (10) in whole-cell cultures grown in trypticase soy broth at 37°C.

  • b β-Lactamase activities (in units per gram of proteins) are the mean values ± standard deviations for at least three different determinations.

  • c β-Lactamase activities were normalized to that of the wild-type promoter for both fusions.