Fig 4.

(A) Effects of purified BpaB and/or EbfC proteins on erp expression in a coupled in vitro transcription/translation system. In the upper panel, product levels were quantified by ELISA and are reported as mean absorbances for three independent experiments. Asterisks indicate statistically significant differences (P < 0.001 by Student's t test) between DNA only and BpaB added, or between BpaB alone and BpaB plus EbfC. The lower panel shows anti-GFP immunoblot analyses of one representative series of in vitro transcription/translation reactions. BpaB significantly repressed erp expression, while addition of EbfC counteracted the repressive effect of BpaB. BSA served as a control to confirm that results were specific for each protein. Addition of rifampin completely prevented product formation, demonstrating that results were dependent upon transcription. (B) Control studies using the B. burgdorferi ospAB promoter and 5′ noncoding DNA fused to gfp. The upper panel shows ELISA results. The lower panel shows anti-GFP immunoblotting results. No added protein or combination of proteins had a significant effect upon expression from the ospAB promoter.