Investigations on stimulation of lac transcription in vivo in Escherichia coli by cAMP analogues

Abstract

The ability of 24 systematically modified analogues of adenosine 3',5'-monophosphate (CAMP) to enhance the synthesis of j?-galactosidase in glucose-repressed Escherichia coli strains KNBL 1001 and cpd-Crookes has been investigated. The properties of the analogues in comparison with cAMP are, with only two exceptions, alike in both strains. Two analogues, 7-deazaadenosine 3',5'-monophosphate (i.e. tubercidin 3',5'-monophosphate) and (RJadenosine 3',5'-monothionophosphate, exhibit higher biological activity than CAMP. The latter analogue is 50-fold more active in both strains. Three analogues showed activities comparable to CAMP, four analogues were less active and 12 analogues were unable to antagonize catabolite repression. Structure-activity correlations showed that the 2'OH-, 3'0-, 5'0-, the negative charge and the 6-amino group cannot be modified without losing biological activity in uivo, while the N-1 and N-7 in adenine are not essential. The interaction with the catabolite gene activator protein is stereoselective for an unmodified axial exocyclic oxygen The molecular mechanism of CAMP action on stimulation of transcription of catabolite-sensitive gene operons was elucidated : a specific cAMP binding protein was isolated and purified. It was named 'catabolite gene activator protein' (CAP) [7] or, alternatively, 'CAMP receptor protein' (CRP) [8]. Regulation by CAP is exerted at the transcriptional level with cAMP acting as an allosteric effector [7,8]. cAMP forms a complex with CAP, thus inducing a conformational change [9], which results in specific recognition of DNA sequences near the promoter of several operons such as lac [lo], gal [ll], araC [12], and increases the rate of transcription initiation. In the lactose [lo] and arabinose operons [12] the CAMP-CAP complex functions as a positive regulator -it potentiates transcription. In the galactose operon, which has two overlapping promoters for RNA polymerase, the complex is required Dedicated to Prof. Dr Friedrich Cramer on the occasion of his 60th birthday.

Role of Protein Kinase A in Collagenase-1 Gene Regulation by Prostaglandin E1: Studies in a Rabbit Synoviocyte Cell Line, HIG-82

“…A recently described isoquinolinesulfonamide compound, H‐89, (42) and an analog of cAMP, RpcAMP, (43) are competitive inhibitors of PKA. Exposure of HIG‐82 synoviocytes to H‐89 over the dose range 30–50 μM for 24 h resulted in an increase in collagenase‐1 message levels (Fig.…”

Opposing Effects on Modulation of Angiogenesis by Protein Kinase C and cAMP-Mediated Pathways

“…We have used two mem brane-permeable analogs of cAMP: Sp-cAMPS and RpcAMPS in order to investigate whether cAMP can modu late angiogenesis. These compounds are more permeable than 8-bromo-cAMP and have much higher specific affin ity for PKA [18], Sp-cAMPS mimicks the effects of natu ral cAMP by dissociating the catalytic subunit, thereby activating the cAMP-dependent protein kinase, whereas Rp-cAMPS binds to the regulatory subunit of the cAMPdependent protein kinase but does not dissociate the cata lytic subunit [40], Thus Rp-cAMPS is a competitive inhibitor for activators of cAMP-mediated signal trans duction [40], These two cAMP analogs have been used extensively in many cell types, including HUVECs, as tools in order to investigate the involvement of the cAMPsignalling pathway in the regulation of cellular functions [11,17,27,[40][41][42], Using these cAMP analogs and forskolin we have dem onstrated in two angiogenesis model systems that the ele vated intracellular levels of cAMP suppress angiogenesis. In the CAM system in ovo, forskolin and Sp-cAMPS caused a dose-dependent suppression of angiogenesis ( fig.…”

Sporulation delay by stable cAMP analogues in the slime moldPhysarum polycephalum

“…In E. eoli the (Rp)-isomer shows much higher biological activity than the (Sp)-analogue (Scholfibbers et al 1984).…”