The Binding of Cyclic Adenosine Monophosphate Receptor to Deoxyribonucleic Acid

The binding of cyclic adenosine 3',5'-monophosphate (cyclic AMP) receptor (CRP) to DNA has been measured by a membrane filter assay and sucrose density gradient analysis. CRP binds to λpgal, λh80dlac ps, calf thymus, salmon sperm, and chicken blood DNA. CRP also binds to denatured chicken blood DNA and the separated strands of λpgal and λplac DNA. The binding of CRP to these DNA species is cyclic AMP-dependent and is inhibited by cyclic guanosine 3',5'-monophosphate. At least 30 molecules of CRP bind to 1 molecule of λpgal DNA as measured by the sucrose density gradient technique. There is no binding of CRP to Escherichia coli RNA polymerase as measured by sucrose density gradient analysis. Although CRP binds to DNA species containing no known CRP-cyclic AMP sensitive promoters, the cyclic AMP dependency of the binding suggests that DNA binding of CRP may be important in stimulation of transcription by CRP-cyclic AMP.