PmrA has been shown to bind the promoters of other PmrA-regulated loci , including pmrCAB , pmrHFIJKLM , and pmrE ( ugd ) ( 1 , 56 ) .
Several PmrA-regulated loci involved in modification of LPS have been identified , including pmrE ( pagA , ugd ) , which encodes a putative UDP-glucose dehydrogenase , and the pmrHFIJKLM operon ( 17 ) .
PmrA has been shown to bind ugd .
Results Mutation of the tolB locus promotes ugd transcription in a phoP-and pmrA-independent manner The ugd gene product participates in multiple cellular activities , suggesting that regulatory systems other than PhoP -- PmrA -- PmrB might also control ugd expression .
Collectively , these results strongly suggest that the pmrC , ugd and pmrG genes and the pbgPE operon are the only PmrA-regulated determinants required for Fe ( III ) resistance .
The absence of transcriptional linkage between the RpoN and the PmrA regulons was corroborated because no significant differences were observed when the expression of PmrAcontrolled genes ( pmrI , pmrC , pmrF , and ugd ) was compared either in a RpoN or in a 1 DrpoN strain grown in LB ( exponential or stationary-phase ) or in a low-Mg N-21 minimal-medium , which are PhoP-and PmrA-inducing conditions ( Soncini & Groisman , 1996 ) ( Fig. 3a and data not shown ) .
( a ) b-Galactosidase activities were determined for pmrI : : MudJ , pmrC : : MudJ , pmrF : : MudJ and ugd : : MudJ ( all PmrA-regulated genes ) in an rpoN ( W-1 t ) or in a DrpoN strain .