PltR transcriptionally activated <i>pltLABCDEFG</i> operon expression <i>via</i> direct binding to the <i>pltLp</i> region from −84 bp to +1.

Abstract

<p>(<b>A</b>) Transcriptional activation of <i>pltLp</i> by PltR. The β-galactosidase expression (Miller Units) from <i>pltLp–lacZ</i> transcriptional fusion (p6522–pltLp) was assayed in M18, M18pltR, M18pltR/pBBR–pltR, and DH5α. The <i>pltLp</i>–<i>lacZ</i> expression was entirely inhibited in the <i>pltR</i> mutant M18pltR, which, in turn, was reversed and even enormously enhanced by the exogenous <i>pltR</i> overexpression from the plasmid pBBR–pltR. (<b>B</b>) Direct binding of PltR to <i>pltLp</i>, assessed by EMSA. 0.5 nM biotin-labelled <i>pltLp</i> promoter fragment (−84 bp to +1) were respectively incubated with increasing amounts of His–PltR protein (0 to 70 μM, Lane 1 to 13). For competition reactions, 0.5 μM unlabeled <i>pltLp</i> fragment was included in the binding reaction in molar as shown in Lane 14. The Hfq protein was used as a negative control (Lane 15).</p