Catabolite Gene Activator Protein: Structure, Homology with Other Proteins, and Cyclic AMP and DNA Binding

The catabolite gene activator protein (CAP), also known as the cyclic AMP (cAMP) receptor protein, is an allosteric protein that functions in the positive and negative regulation of the catabolite operons, as well as many other operons in Escherichia coli (Zubay et al. 1970; Epstein et al. 1975). In the presence of cAMP, CAP binds to specific sites near promoters and switches on transcription by RNA polymerase. CAP binds only nonspecifically to DNA in the absence of cAMP. We are interested in addressing three questions in our structural studies of CAP: (1) What is the nature of the allosteric transition induced by cAMP that changes CAP from a protein that binds to DNA nonspecifically to one that can recognize a specific nucleotide sequence? (2) How does the CAP complex with cAMP recognize a specific nucleotide sequence? (3) How does the binding of this CAP complex to its specific DNA-binding site...