Cyclic adenosine monophosphate receptor: loss of cAMP-dependent DNA binding activity after proteolysis in the presence of cyclic adenosine monophosphate.

The cAMP receptor requires cAMP for DNA binding at pH 8.0 but shows cAMP-independent DNA binding at pH 6.0. Incubation of the cAMP receptor with proteolytic enzymes in the presence of cAMP results in loss of DNA-binding ability at pH 8, while it is still able to bind cAMP and DNA at pH 6. Incubation with proteolytic enzyme in the absence of cAMP does not affect the DNA-binding properties of the cAMP receptor. After proteolysis in the presence of cAMP, analysis by sodium dodecyl sulfateacrylamide-gel electrophoresis shows that the 22,500-dalton subunit characteristic of the untreated protein has been completely replaced by a 12,500-dalton fragment.