CAMP receptor

Gorshkova, I., J.L. Moore, K.H. McKenney, and F.P. Schwarz. 1995. Thermodynamics of cyclic nucleotide binding to the cAMP receptor protein and its T127L mutant. J Biol Chem 270 21679-21683. 

D. Dormann, J. Y. Kim, P. Devreotes, and C. J. Weijer, cAMP receptor affinity controls wave dynamics, geometry and morphogenesis in Dictyostelium. J. Cell. Sci. 114, 2513-2523 (2001). 

PDE hydrolyzes cAMP. Receptor kinase phosphorylates OR, inactivating it. Odorant is removed by metabolism. 

Two types of G protein-coupled cAMP receptors in the cell membranes of the amebas have been identified. One leads to activation of adenylate cyclase and the release of new pulses of cAMP and the other to activation of guanylate cyclase.6 This enzyme causes a rapid 7- to 10-fold increase in intracellular cGMP which plays an important role in controlling chemotaxis. 

In all cases the cells also utilize cAMP as an internal second messenger. For D. discoideum the components of the chemotactic-aggregation system include a 41-kDa cAMP receptor on the outside, adenylate cyclase, an extracellular diesterase that specifically hydrolyzes the cAMP to AMP, and a diesterase inhibitor protein.35 227-230 The inhibitor keeps the phosphodiesterase largely inactive initially, but when cAMP concentrations build up synthesis of the inhibitor is repressed and the cAMP is hydrolyzed, a necessary condition for retaining sensitivity of the receptors for the arriving pulses of cAMP. 

Catabolite activator protein, CAP (also called cAMP receptor protein, CRP) is an activator required for high level transcription of the lac operon. The active molecule is a CRP dimer that binds 3 5 cyclic AMP to form a CRP-cAMP complex. CRP-cAMP binds to the lac promoter and increases the binding of RNA polymerase, stimulating transcription of the lac operon. CRP dimer without cAMP cannot bind to this DNA. The action of CRP depends upon the carbon source available to the bacterium. When glucose is present, the intracellular level of cAMP falls, CRP cannot bind to the lac promoter and the lac operon is only weakly transcribed. When glucose is absent, the level of intracellular cAMP rises, the CRP-cAMP complex stimulates transcription of the lac operon and allows lactose to be used as an alternative carbon source. 

The stability of the reagent to the assay conditions should also be ascertained. The instability of azides and diazo compounds towards thiols was mentioned earlier, and it would be prudent to ensure that all new reagents whether they contain familiar photoactivatable groups or not are stable to the prevailing chemical and enzymatic conditions. In an attempt to label the cAMP receptor of D. discoideum, Wallace and Frazier (1979b) found that 8-N rcAMP was converted to NrAMP by the phosphodiesterase of a crude membrane preparation. The NrAMP specifically labeled actin and not the cAMP receptor. 

Substrate for cAMP PDE (activates PKA, opens cAMP-gated Na+ channels binds to Dictyostelium cAMP receptor)... 

CRP C-reactive protein also cAMP receptor protein... 

Eleyduk T, Lee JC. Escherichia-coli camp receptor protein - evidence for 3 protein conformational states with different promoter binding affinities. Biochemistry 1989 28 6914-6924. 

Elarman JG. Allosteric regulation of the cAMP receptor protein. Bba-Protein Struct. M 2001 1547 1-17. 

CMP Camp receptor protein (catabolite activator protein)... 

A water-soluble cyclic AMP (cAMP) receptor (Figure 57) has been reported by Rebek and coworkers [79]. Both 2, 3 -cAMP and 3, 5 -cAMP were shown to bind to this receptor with association constants of 660 and 600 M ,... 

Chemoattractant is used to demonstrate signal-induced gradient of Gp subunit. False color Images of amebas expressing (a) a GFP-tagged Gp subunit and (b) a GFP-tagged cAMP receptor, which served as a control. When an external source of chemoattractant was placed near the cells (at the top of the photographs), the cells turned toward the source. 

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