<p>(<b>A</b>) Construction map of the mutagenized <i>pltLp</i> with <i>lys</i> box mutations. Three <i>pltLp</i> mutant fragments, <i>pltLp-M2</i>, <i>-M4</i>, and <i>-M6</i>, respectively carried 2 bp, 4 bp, and 6 bp replacements in the <i>lys</i> box. The <i>pltLp</i> mutant M4-M was constructed by introducing a 4 bp complementary replacement into the <i>pltLp-M4</i> mutant. The above four <i>pltLp</i> mutagenized fragments were respectively cloned into pME6522. (<b>B</b>) β-galactosidase expression (Miller Units) from the above <i>lacZ</i> fusion plasmids was measured in the M18 strain. The <i>pltLp</i> expression gradually and significantly decreased, even entirely inhibited, with the opening of the <i>lys</i> box formed stem loop (Fig. 4A) by base substitutions. (<b>C</b>) The binding of PltR to <i>pltLp</i> was significantly weakened and even eliminated by the <i>lys</i> box mutations. <i>pltLp</i> and its derivative mutated fragments (0.5 nM) were respectively incubated with increasing amounts of PltR protein. The concentration of PltR was 0, 10, and 60 μM, respectively.</p
