| Popis: |
Several analogues of cyclic adenosine 3',5'-monophosphate (cyclic AMP) have been tested for their ability to inhibit the binding of cyclic AMP to cyclic AMP receptor (CRP) and to inhibit the cyclic AMP-CRP-dependent transcription of the gal operon. A number of the cyclic AMP derivatives are able to inhibit cyclic AMP binding to CRP, but of all the analogues studied only tubercidin 3',5'-monophosphate is able to replace cyclic AMP in promoting gal transcription. Those analogues which inhibit cyclic AMP binding also decrease cyclic AMP-CRP-dependent transcription. Derivatives with a modified cyclic phosphate structure are potent inhibitors of gal transcription although they do not influence cyclic AMP binding to CRP as observed in the ammonium sulfate precipitation assay. These results indicate a marked specificity for cyclic AMP in stimulating gal mRNA synthesis and also point to the probability that the purine base, the ribose moiety, and the cyclic phosphate group all are involved in binding to CRP and eliciting the correct conformational change of the protein required to mediate cyclic AMP-dependent gene transcription. |
