A positive repression process in cellular transcription, in which RNA polymerase binds poorly to the operon's promoter. The binding of CRP and cAMP to the promoter causes RNA polymerase to bind more effectively and initiate transcription. Active constituents of this process are cAMP and CRP.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.