title: Probing the sequence-specific interaction of the cyclic AMP receptor protein with DNA by site-directed mutagenesis.
abstract: Mutants in the DNA-binding helix of the cyclic AMP receptor protein (CRP), as well as mutants in a synthetic DNA-binding site derived from the sequence in the lac regulatory region, have been constructed by oligonucleotide-directed mutagenesis, and used to study the effect of selected amino acid substitutions on CRP-mediated transcriptional activity and on sequence-specific DNA binding. It has been shown that mutation of Arg-180 to Lys or Leu abolishes both CRP-mediated expression of beta-galactosidase in vivo and CRP binding of DNA as measured by immunoprecipitation. In contrast, the mutation of Arg-185 to Leu or Lys and the mutation of Lys-188 to Leu does not appear to influence these two parameters significantly. On the DNA side, both substitutions studied, namely the exchange of the G . C base pair in position 2 of the consensus T1G2T3G4A5 motif into an A . T base pair and the exchange of the A . T base pair in position 5 for a G . C base pair, abolish specific binding. Implications of these findings with respect to the present models for specific CRP-DNA recognition are discussed.
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D011232:Chemical Precipitation; D004247:DNA / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D009154:Mutation; D011953:Receptors, Cyclic AMP / Q000235:genetics* / Q000276:immunology; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D011953:Receptors, Cyclic AMP; D004247:DNA; D001616:beta-Galactosidase