Mechanism for transcriptional action of cyclic AMP in Escherichia coli: entry into DNA to disrupt DNA secondary structure.

Publisher Website
Google Scholar
Abstract
Binding analysis with purified bacterial receptor distinguishes 2 structural domains in cAMP. The 1st, the cyclic phosphate and furanose, constitutes a binding domain. This region is bound tightly to the receptor. The rest of cAMP is not bound; the adenine moiety of cAMP is exposed. Unlike binding, activity of cAMP requires the adenine moiety. To be active, cAMP must have in domain II the base adenine, specifically, its Watson-Crick atoms N-1 and N-6. Analysis of IAA, a compound able to replace cAMP at the L-arabinose operon, indicates a similar distinction between binding and active domains. To be active, the indole must have substitution (carboxyl or amide) electronically comparable to the cAMP N-1 and N-6. On this basis, a detailed mechanism for action of cAMP (or IAA) in E. coli is proposed. The exposed adenine of cAMP enters into the DNA. N-1 and N-6 of adenine form hydrogen bonds to a thymine in DNA. This interaction destabilizes the DNA. It enhances transcription. Marked similarities indicate an identical mechanism for the steroid hormones in eukaryotes.