To determine whether the PmrA-regulated genes identified herein affect lipid-A structure ( particularly for STM4118 , which demonstrated somewhat decreased PM resistance ) , purified lipid-A from each mutant ( PmrA background ) was compared to that of the C parental strain for the presence of Ara4N .
Using site directed mutagenesis , Marchal et al. demonstrated that the fifth positions of the first hexameric repeat are essential for binding by PmrA ; these are conserved in the STM4118 promoters .
Using site directed mutagenesis , Marchal et al. demonstrated that the third positions of the first hexameric repeat are essential for binding by PmrA ; these are conserved in the STM4118 promoters .
Here we demonstrate that the PmrA-regulated STM4118 ( cptA ) gene is necessary for the addition of pEtN to the LPS core .