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 STM1253 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 STM1253 promoters .