It accepts a methyl group from methylphosphotriesters and then acts as a transcriptional activator of the ada operon AdiY Escherichia coli SP : P33234 Transcriptional activator of the adiA gene for 253 32 , 237 biodegradative acid-induced arginine decarboxylase AfrR Escherichia coli TE : Q07681 Probable transcriptional activator of the 272 258 afrABRS operon for expression of AF/R1 fimbria in E. coli RDEC-1 , a rabbit pathogen AggR Escherichia coli SP : P43464 Transcriptional activator of the aggA gene for 265 183 aggregative adherence fimbria I ( AAF/I ) expression in enteroaggregative E. coli strains AppY Escherichia coli SP : P05052 Transcriptional activator of the cyxAB , hyaAB-243 12 , 131 CDEF and appA operons during the deceleration phase of growth AraC Citrobacter freundii SP : P11765 Regulator of several operons involved in the 281 30 transport and catabolism of L-arabinose ( similar to E. coli AraC ) AraC Escherichia coli SP : P03021 Activator of the expression of the araBAD , 292 174 , 238 , 248 , 266 araFGH and araE operons , which are involved in the transport and catabolism of L-arabinose .