The PmrA training set consisted of the promoter regions of three known PmrAB-regulated genes ( ugd [ 7,15,17 ] , pmrH [ 7,14,17,19 ] and pmrC [ 2,14 ] ) for which the binding of the PmrA protein to the promoter regions was verified by DNA footprint analysis [ 14,15 ] .
However , Lee et al. [ 21 ] demonstrated that the loss of pmrC and the pmrHFIJKLM operon ( also called the pbg operon ) resulted in PM resistance equal to that of a pmrA mutant strain , suggesting a limited role for PmrAB-regulated core modification in PM resistance .
PmrAB-regulated genes include pmrHFIJKL , whose product results in the addition of aminoarabinose to the 1 and 4 = phosphates of lipid-A ( D ) ; pmrC , whose product results in the addition of phosphoethanolamine to the 1 and 4 = phosphates of lipid-A ( E ) ; cptA , whose product results in the addition of phosphoethanolamine to the LPS core ( F ) ; pmrG , whose product results in the addition of phosphate to heptose present in the LPS core ( G ) ; and cld , whose product results in an O-antigen chain length determinant ( H ) .