A computer aided oligonucleotide analysis provides a model sequence for RNA polymerase-promoter recognition in E.coli

A novel computer procedure has been used to search for homology among 17 known procaryotic promoter sequences. A model sequence, :formula: (see text), is compatible with the properties of all known promoter and operator mutations, predicts base positions for the initiation of RNA synthesis coinciding with those determined experimentally, is compatible with current models for the regulation of transcription, suggests that RNA polymerase could recognize the DNA double helix firstly in the B conformation then in the A.

The cyclic 3',5'-adenosine monophosphate receptor protein and regulation of cyclic 3',5'-adenosine monophosphate synthesis in Escherichia coli

Rates of synthesis of cyclic 3',5'-adenosine monophosphate (cAMP) were measured in cultures of Escherichia coli aerating without a carbon source. This technique provides a representative measure of adenylate cyclase activity in the absence of inhibition caused by transport of the carbon source. Adenylate cyclase activity was found to vary more than 20-fold depending on the carbon source that had been available during growth. Synthesis of cAMP in cells aerating in the absence of the carbon source was highest when cells had been grown with glucose or fructose which inhibit adenylate cyclase activity severely. Synthesis of cAMP was much lower when cells had been grown with glycerol or succinate which cause only minimal inhibition of the activity. The variation in cAMP synthesis due to different carbon sources requires a functional cAMP receptor protein (CRP). Crp- mutants synthesize cAMP at comparable rates regardless of the carbon source that afforded growth. A novel mutant of E. coli having a CRP no longer dependent on cAMP has been isolated and characterized. Adenylate cyclase activity in this mutant no longer responds normally to variations in the carbon source.

Adenosine 3':5'-monophosphate receptor proteins in mammalian brain

cAMP receptor proteins present in mammalian brain were identified and characterized with the use of the photoaffinity label 8-azido[32P]cAMP. Cytosol and membrane fractions from various regions of rat, guinea pig, and bovine brain contained two specific cAMP receptor proteins with apparent molecular weights of 47,000 and 52,000 to 55,000. Subcellular fractionation studies showed the highest amounts of these cAMP receptor proteins associated with cytosol fractions and synaptic membrane fractions. For both the cytosol and membrane fractions, the two cAMP receptor proteins represented almost all of the proteins specifically labeled by 8-azidol[32P]cAMP and appeared to be the regulatory subunits of cAMP-dependent protein kinases.

Determination of the rates of synthesis and degradation of adenosine 3',5'-cyclic monophosphate in Escherichia coli CRP- and CRP+ strains

We have developed a method for estimating the rates of synthesis and degradation of adenosine 3',5'-cyclic monophosphate (cAMP) in Escherichia coli during balanced growth. Applying this method, we have found that an E. coli CRP- mutant 5333 (deficient for cAMP receptor protein) synthesizes cAMP about 25 times faster than does its CRP+ parent 1100. This accounts for the abnormally high intracellular and extracellular cAMP accumulation in 5333.

A rapid high-yield purification procedure for the cyclic adenosine 3',5'-monophosphate receptor protein from Escherichia coli

A new method for the purification of the cyclic adenosine 3',5'-monophosphate receptor protein from Escherichia coli has been developed. The method is rapid and simple, and a very high yield of the purified protein is obtained which is not contaminated with either DNAase or RNAase activity.

Adenosine 3':5'-cyclic monophosphate-dependent protein kinase(s) of rat ovarian cells. Gonadotropin regulation of adenosine 3':5'-cyclic monophosphate-receptor activity

Regulation of cyclic AMP-dependent protein kinase, cyclic AMP-receptor activity and intracellular cyclic AMP concentrations by choriogonadotropin was studied in ovarian cells prepared from 26-day-old rats. A close correlation was observed between phospho-transferase activity and cyclic AMP-receptor activity in 12000g supernatant fractions from rat ovarian homogenate. The apparent activation constant (K(a)) and I(50) (concentration required to produce 50% inhibition) of different cyclic nucleotides for phosphotransferase and cyclic AMP receptor activities respectively were also determined. Cyclic AMP and 8-bromo cyclic AMP were most effective, giving K(a) values of 0.08 and 0.09mum and I(50) of 0.12 and 0.16mum respectively. Other nucleotides were also effective, but required higher concentrations to give a comparable effect. An increased concentration of cyclic AMP produced by choriogonadotropin (1mug/ml) treatment was accompanied by decreased cyclic AMP binding as early as 5min after hormone addition. Choriogonadotropin also stimulated the protein kinase activity ratio (-cyclic AMP/+cyclic AMP) under identical experimental conditions. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine potentiated the action of choriogonadotropin on the three parameters measured in a dose- and time-dependent manner. The maximal cyclic AMP-binding capacity, as determined by cyclic AMP-exchange assay, remained unchanged before and after hormone addition. The endogenously bound cyclic AMP was determined from the difference between the maximal binding capacity and the exogenously bound cyclic AMP. With different choriogonadotropin concentrations, a quantitative correlation was established between maximal binding capacity, exogenous binding and endogenous binding activities. Approx. 60% of total binding sites were endogenously occupied in untreated cells, and choriogonadotropin (1mug/ml) treatment fully saturated available binding sites with a parallel 10-fold increase in cellular cyclic AMP. The present results provide evidence for a probable intracellular compartmentalization of cyclic AMP in the ovarian cell, and suggest that in the unstimulated state all cyclic AMP present in the ovarian cell may not be available for protein kinase activation.

A new extragenic suppressor of cya mutation. Mutant cyclic AMP receptor protein with an increased affinity for cyclic AMP

A strain bearing an extragenic suppressor of cya mutation was isolated as a second-site revertant of an adenylate cyclase deficient strain. The mutant was unable to synthesize cAMP but showed normal fermentation profiles and growth properties on a variety of carbon sources. The site of reversion was mapped in, or near, the structural gene for the cAMP receptor protein. Structural alteration of the protein was directly demonstrated by the following biochemical observations: (i) A 10-fold decrease in the dissociation constant for cAMP, (ii) an acidic shift in the isoelectric point, and (iii) the altered binding properties to lambdah80dlac ps DNA.

Catabolite repression in Escherichia coli mutants lacking cyclic AMP

The regulation of catabolite repression of beta-galactosidase has been studied in Escherichia coli mutants deleted for the adenyl cyclase gene (cya delta), and thus unable to synthesize cyclic AMP. It has been found that, provided a second mutation occurs either in the crp gene coding for the catabolite gene activator protein (CAP) or in the Lactose region, these mutants exhibit catabolite repression. If the catabolite repression seen in the mutant strains corresponds to the mechanism operating in wild-type cells the results would suggest that the intracellular concentration of cyclic AMP cannot be the unique regulator of catabolite repression.

The dependence of Escherichia coli asparaginase II formation on cyclic AMP and cyclic AMP receptor protein

The amount of asparaginase II in an Escherichia coli wild-type strain (cya+, crp+) markedly increased upon a shift from aerobic to anaerobic growth. However, no such increase occurred in a mutant (cya) lacking cyclic AMP synthesis unless supplemented with exogenous cyclic AMP. Since a mutant (crp) deficient in cyclic AMP receptor protein also did not support the anaerobic formation of this enzyme, it is concluded that the formation of E. coli asparaginase II depends on both cyclic AMP and cyclic AMP receptor protein.

Adenosine 3', 5'-cyclic monophosphate-binding proteins from Trypanosoma gambiense

Two cyclic AMP-binding proteins, not identical with regulatory subunits of protein kinases, have been isolated from Trypanosoma gambiense. The cyclic AMP receptors were separated by gel chromatography on the basis of their molecular weights. The binding constants of the high and the low molecular weight receptors for cyclic AMP were determined to be 0.4 muM and 0.6 muM, respectively. Cyclic IMP and cyclic GMP compete with cyclic AMP for the binding sites of both receptors. The cyclic AMP binding of the low molecular weight receptor was competitively inhibitied by adenine derivatives. The binding capacity of the high molecular weight receptor was enhanced about two-fold by proteolytic modification with trypsin.

Physiological and biochemical characterization of aggregation-deficient mutants of Dictyostelium discoideum: detection and response to exogenous cyclic AMP

Forty independently isolated aggregation-deficient (Agg−) mutants of Dictyostelium discoideum, which have been partially characterized genetically, were examined for the ability to respond chemotactically to exogenous cAMP and for certain cellular and extracellular activities thought to be involved in this process. Only five of the mutants failed to produce a statistically significant chemotactic response to cAMP. When shaken in buffer, most of the Agg− mutants produced reduced levels of the cAMP-binding sites and the cell-bound cAMP phosphodiesterase reported to be components of a cell-surface cAMP receptor involved in the chemotactic response. In addition, most of the mutants failed to form contact sites A and were unable to develop on water agar plates. When the mutants were pulsed with 100 nM cAMP, 36 of 40 mutants produced detectable contact sites A and three-quarters of these strains underwent further development when placed on a solid substratum. Treatment with cAMP pulses also stimulated certain mutants to form higher levels of cAMP receptors. These observations suggest that the impaired differentiation of the plasma membrane of many Agg− mutants is due, at least in part, to the abnormal synthesis and (or) secretion of cAMP by these strains. When grown in bacterial suspension, all 40 of the mutants produced extracellular phosphodiesterase (ePD) activity, and all but 8 of the mutants secreted detectable amounts of the ePD inhibitor. In general, Agg− strains carrying mutations at the same aggregation locus (aggF–J) exhibited very similar physiological and biochemical properties.

Presence of the sites for interacting with cyclic AMP and with catalytic subunit on small fragments of protein kinase regulatory subunit

During the purification of cyclic AMP binding proteins from rat liver, some smaller active fragments were obtained, possibly as the result of proteolysis. The binding proteins detected had approximate molecular weights of 50,000, 36,000, and 10,000. Each of these components bound cyclic [3H]AMP with high affinity (apparent dissociation constants ranging from 2 to 10 nM) and had a similar ability to inhibit the purified catalytic subunit of rat liver protein kinase. Cyclic AMP prevented this inhibition in each instance. These results suggest that the binding site for cyclic AMP and the site for interacting with catalytic subunit occur relatively close to one another on the regulatory subunit and can remain functional when a substantial fraction of the subunit is lost.

Differential activation of type-I and type-II adenosine 3':5'-cyclic monophosphate-dependent protein kinases in liver of glucagon-treated rats

The protein-bound cyclic AMP and the activity of cytosolic protein kinases in the presence and absence of cyclic AMP were determined in rat liver up to 2h after injection of glucagon. On the basis of the different salt-sensitivities of the activated cyclic AMP-dependent proteinkinases I and II, an activation of protein kinase II restricted to the high cyclic AMP concentrations present in the first 30 min after hormone injection was found. Essentially the same result was obtained by chromatographic analysis on DEAE-cellulose of liver cytosol from untreated rats and from rats killed at 2 and 60 min after glucagon injection. Protein kinase II activation was only detected at 2 min after injection. In contrast, the cyclic AMP-dependent protein kinase I was found to be nearly totally activated at 2 min and to be still almost as active at 60 min after the hormone stimulus, whereas the amount of bound cyclic AMP and the activation of total cytosolic protein kinases had fallen to two-thirds of their maximal values during this time period. A third cyclic AMP-independent protein kinase, which co-chromatographed with protein kinase type II, could be clearly distinguished from the two cyclic AMP-dependent kinases by use of the heat-stable inhibitor from bovine muscle, which totally inhibited the cyclic AMP-dependent enzymes, but stimulated the cyclic AMP-independent protein kinase.

Human erythrocyte proteins associated with adenosine 3',5'-cyclic monophosphate action

Two adenosine 3',5'-cyclic monophosphate (cyclic-AMP)-binding protein factors (molecular weight 230,000) have been partially purified from human erythrocytes. One of these proteins seems to be different from the cyclic-AMP-binding component of the cyclic-AMP-dependent protein kinases. These protein factors are also capable of binding adenosine. We present data also on two forms of cyclic-AMP-dependent protein kinases (ATP: protein phosphotransferase, EC 2.7.1.37) partially purified from the cytosol of normal human erythrocytes. Kinase I has been classified as type I enzyme on the basis of its activation when preincubated with protamine, histone or NaCl. The substrate specificities of the two kinases and many of their kinetic parameters are rather similar. Their subunit structure is reminiscent of that of kinases obtained from other sources. The catalytic subunit of both enzymes reversibly cross-react with the regulatory subunit of kinase I from the rabbit red blood cell.

Species-specific aggregation factor in sponges. VII. Its effect on cyclic amp and cyclic gmp metabolism in cells of Geodia cydonium

In dissociated single cells from the sponge Geodia cydonium, DNA synthesis is initiated after incubation with a homologous, soluble aggregation factor. During the DNA-initiation phase the cyclic AMP- and cyclic GMP levels vary drastically; the cyclic AMP content drops from 2.2 pmol/10(6) cells to 0.3 pmol/10(6) cells while the cyclic GMP content increases from 0.6 pmol to 3.7 pmol/10(6) cells. The activity of neither the adenylate cyclase nor of the guanylate cyclase isolated from cells which have been incubated for different periods of time with the aggregation factor, is changed. The soluble as well as the particulate enzyme activities were checked in vitro. The cyclic nucleotide receptors have been isolated from the sponge cells and characterized with respect to their molecular weight, dissociation constant for cyclic AMP or cyclic GMP and intracellular concentration. None of these parameters are altered during aggregation factor-mediated DNA initiation. From these data it is concluded that the regulation of cyclic nucleotide levels is a consequence of a changed activity of nucleotide cyclases or of phosphodiesterases, but this is presumably not caused by a changed rate of synthesis of nucleotide cyclases or of cyclic nucleotide receptors.

Adenylyl cyclase and the control of cell differentiation in Dictyostelium dicoideum

Adenylyl cyclase is part of a biochemical network that controls cell differentiation in Dictyostelium discoideum. At a certain stage of development the enzyme is rhythmically activated, with periods of about 8 min. These oscillations are superimposed upon an increase of the basal activity extending over a period of hours. The basal activity remains low in a mutant blocked at an early stage of development. In strain Ax-2 two periods of strongly increasing basal activity have been found: the first from 2 to 4 h after the end of the growth phase, the other beginning at about 8 h. Based on the periodic regulation of adenylyl cyclase, cyclic AMP is released into the extracellular space in the form of pulses. Application of cyclic-AMP pulses, but not its continuous influx, stimulates the increase of basal adenylyl cyclase activity. Two other constituents of the cyclic-AMP signal system cyclic-AMP receptors and cell-surface phosphodiesterase, are similarly controlled. The principal importance of positive feedback loops in a network controlling cell differentiation is discussed.

Identification, characterization, and quantitative measurement of cyclic AMP receptor proteins in cytosol of various tissues using a photoaffinity ligand

Two protein bands, present in cytosol fractions from each of seven rat tissues examined, specifically incorporated 32P-labeled 8-azidoadenosine 3':5'-monophosphate (8-N3-[32P]cAMP), a photoaffinity label for cAMP-binding sites. These proteins had apparent molecular weights of 47,000 and 54,000 on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis system. These two proteins were characterized in three of the tissues, namely, heart, uterus, and liver, by the total amount of 8-N3-[32P]cAMP incorporation, by the dissociation constant (Kd) for 8-N3-[32P]cAMP, and by the nucleotide specific inhibition of 8-N3-[32P]cAMP incorporation. Several lines of evidence were obtained that the protein with an apparent molecular weight of 47,000 represents the regulatory subunit of a type I cAMP-dependent protein kinase, while the protein with an apparent molecular weight of 54,000 represents the regulatory subunit of a type II cAMP-dependent protein kinase. Almost all of the cAMP receptor protein found in the cytosol of these tissues, as measured by 8-N3-[32P]cAMP incorporation, was associated with these two protein kinases, in agreement with the idea that most effects of cAMP are mediated through protein kinases. The photoaffinity labeling with 8-N3-[32P]cAMP can be used to estimate quantitatively the amounts of regulatory subunit of type I and type II cAMP-dependent protein kinases in various tissues.

Binding proteins for adenosine 3':5'-cyclic monophosphate in bovine adrenal cortex

Five peaks of cyclic AMP-binding activity could be resolved by DEAE-cellulose chromatography of bovine adrenal-cortex cytosol. Two of the binding peaks co-chromatographed with the catalytic activities of cyclic AMP-dependent protein kinases (ATP-protein phosphotransferase, EC 2.7.1.37) of type I or type II respectively. A third binding protein was eluted between the two kinases, and appeared to be the free regulatory moiety of protein kinase I. Two of the binding proteins for cyclic AMP, sedimenting at 9S in sucrose gradients, could also bind adenosine. They bound cyclic AMP with an apparent equilibrium dissociation constant (K(d)) of about 0.1mum, and showed an increased binding capacity for cyclic AMP after preincubation in the presence of K(+), Mg(2+) and ATP. The two binding proteins differed in their apparent affinities for adenosine. The isolated regulatory moiety of protein kinase I had a very high affinity for cyclic AMP (K(d)<0.1nm). At low ionic strength or in the presence of MgATP, the high-affinity binding of cyclic AMP to the regulatory subunit of protein kinase I was decreased by the catalytic subunit. At high ionic strength and in the absence of MgATP the high-affinity binding to the regulatory subunit was not affected by the presence of catalytic subunit. Under all experimental conditions tested, dissociation of protein kinase I was accompanied by an increased affinity for cyclic AMP. To gain some insight into the mechanism by which cyclic AMP activates protein kinase, the interaction between basic proteins, salt and the cyclic nucleotide in activating the kinase was studied.

DNA-directed synthesis in vitro of beta-galactosidase: requirement for a ribosome release factor

The DNA-directed synthesis of beta-galactosidase in Escherichia coli extracts has been investigated in a partially fractionated system. A dependency was obtained for 3',5'-cyclic AMP receptor protein and also for a factor, from the salt wash of ribosomes, that has been purified to near homogeneity. This factor has been identified with a ribosome release factor previously purified from the supernatant fraction by A. Hirashima and A. Kaji [(1972) Biochemistry 11,4037-4044]. In the coupled transcription-translation system this factor stimulates beta-galactosidase synthesis and total protein synthesis 2- to 4-fold. It is thus clear that the ribosome release factor has a physiological function in translation. It may also affect transcription, because it stimulated total RNA synthesis up to 50% in this in vitro system.

Intermediate role of adenosine 3':5'-cyclic monophosphate and protein kinase during gonadotropin-induced steroidogenesis in testicular interstitial cells

Discrepancies between adenosine 3':5'-cyclic monophosphate (cAMP) and steroid production have been frequently observed in isolated target cells stimulated by low concentrations of trophic hormone. This dissociation is particularly marked in the interstitial cells of the testis, where testosterone production is elicited by gonadotropin concentrations in the picomolar range. Because of these observations, and a disparity between steroidogenesis and protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) activation in Leydig cells, the role of cAMP as a mediator of the acute steroidogenic response has been questioned. This problem has been further analyzed by assay of free and occupied cAMP-binding sites of the regulatory subunit of protein kinase in basal and hormone-stimulated cells. Free sites were measured by a [(3)H]-cAMP-binding assay, and occupied sites were measured by radioimmunoassay of endogenous cAMP eluted from receptor protein. After stimulation of purified Leydig cells with 0.1-10 pM human chorionic gonadotropin, a dose-dependent decrease in available [(3)H]cAMP-binding sites was observed, with no change in binding affinity. The reduction in cAMP-binding sites was equivalent to the increase in occupancy of cAMP receptors by endogenous nucleotide formed during gonadotropin action. Fractional occupancy of cAMP receptors rose progressively from basal values of 0.2-0.40 to full saturation as intracellular cAMP rose 10- to 30-fold during hormone stimulation. The testosterone dose-response curve was coincident with the initial part of the cAMP-receptor occupancy curve. These changes in endogenous cAMP binding to the regulatory subunit were accompanied by a significant increase in protein kinase activity in gonadotropin-stimulated Leydig cells. These observations provide direct evidence for the role of cAMP and protein kinase during hormonal activation of steroidogenesis in the Leydig cell by low concentrations of gonadotropin.

Effects of cyclic nucleotides on the conformational states of the alpha core of the cyclic AMP receptor protein

The alpha core gragment produced by limited proteolysis contains the cyclic AMP binding domain and the two buried sulfhydryl groups of the cyclic AMP receptor protein. The buried sulfhydryl groups of the alpha core react with 5,5'-dithio-bis(2-nitrobenzoic acid) after denaturation by 3 M urea or digestion with subtilisin. The rate of sulfhydryl modification in the presence of 3 M urea or subtilisin is markedly decreased in the presence of cyclic nucleotides which are proposed to tighten the conformation of the alpha core. Incubation of the alpha core in 3 M urea or dithionitrobenzoic acid does not affect cyclic AMP binding while dithionitrobenzoic acid plus 3 M urea inhibits cyclic AMP binding suggesting a role for the buried sulfhydryls in cyclic AMP binding or their proximity to the cyclic AMP binding domain of the alpha core. The data are consistent with a ligand-induced conformational change in the alpha region of the native cyclic AMP receptor protein that is required for DNA binding.

A hypothesis concerning the structure of cAMP-and cGMP-dependent protein kinases

cAMP-and cGMP-dependent protein kinases have been purified. Each enzyme demonstrates high specificity and affinity for the cyclic nucleotide with binding of two moles of nucleotide per holoenzyme and each enzyme is an ATP: phosphotransferase. The holoenzymes have similar molecular weights and demonstrate similar molecular asymmetry. A structural model relating the two enzymes is proposed. cGMP-dependent protein kinase is proposed to be a dimer composed of two identical protomers in isologous association with the chains arranged in anti-parallel fashion. cAMP-dependent protein kinase is proposed to have a similar structure with a dyad axis of symmetry but with a discontinuity in each chain. These structures account for the differing mechanisms of cyclic nucleotide activation of the two enzymes.

Determination of the nucleotide sequence of part of the regulatory region for the galactose operon from Escherichia coli

We have determined the sequence of 59 base pairs in the DNA preceding the site for initiation of transcription in the galactose operon. DNA from a lambdagal transducing phage was digested with restriction endonucleases to obtain a DNA fragment from the gal regulatory region. This fragment extends from 59 base pairs prior to the transcription initiation site through the 45 base pairs which specify the 5'-terminal sequence of gal mRNA. Analyses of RNA transcripts derived from this fragment and a variety of direct DNA sequence analyses allowed us to deduce the following sequence for the DNA in this fragment: (formula: see text) Position +1 corresponds to the site for initiation of gal mRNA synthesized in the presence of cyclic AMP and its receptor protein, CRP. Transcription experiments indicate, however, that this fragment lacks some element of the gal promoter required for the stimulation of transcription by CRP-cAMP. There are, nonetheless, some similarities between the gal sequence preceding the transcription start site and the sequences of other promoter regions. These include the heptamer sequence T-A-T-G-G-T-T (--12 to --8) and the sequence A-C-A-C-T-T-T (--36 to --30).

Purification of phosphoprotein phosphatase from bovine cardiac muscle that catalyzes dephosphorylation of cyclic AMP-binding protein component of protein kinase

A phosphoprotein phosphatase that catalyzes the dephosphorylation of cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase from bovine cardiac muscle has been purified to homogeneity by a modification of the procedure of Brandt et al. (Brandt, H., Capulong, Z.L., and Lee, E. Y. C. (1975) J. Biol. Chem. 250, 8038-8044). Treatment of the enzyme preparation with ethanol during the early stages of purification results in activation concomitant with reduction in molecular weight to 30,000. The purified activated enzyme has a Km for phospho-protein kinase in the presence or absence of 1.2 mM Mn2+ of 5 and 22 micronM, respectively. Phosphatase activity on phospho-protein kinase but not on other phosphoprotein substrates was cAMP-dependent. This selective activation by cAMP reflects the preference of the phosphatase for the free, phosphorylated cAMP-binding protein rather than the phosphoholoenzyme.

Calcium ion effects on cyclic adenosine 3':5'-monophosphate bindings to the plasma membrane of Dictyostelium discoideum

The study of cell surface cyclic adenosine 3':5'-monophosphate binding to Dictyostelium discoideum amoebae indicates that Ca2+ increases the number of binding sites without significantly affecting their affinity constant(s). The effects of the ion are observed immediately (within 4 s after addition) and appear to be readily reversible. Ca2+ effects are observed at various temperatures and pH values and are not blocked by the presence of various metabolic inhibitors. Increases, and decreases, in the apparent number of cyclic nucleotide binding sites could also be effected by concanavalin A treatments which respectively stimulate, and inhibit cell differentiation.

Differential binding of cyclic adenosine 3' ,5'-monophosphate to the cyclic adenosine 3' ,5'-monophosphate receptor protein in Escherichia coli

Binding of cyclic adenosine 3' ,5'-monophosphate (cAMP) by the cAMP receptor protein in crude cell-free extracts of Escherichia coli was characterized. When cell were grown in glucose, binding was inhibited 50% relative to extracts from cells grown with succinate as carbon source . This inhibition could be relieved by dialysis.

Use of a competitive protein-binding assay for adenosine 3':5'-phosphate for the study of bovine corpus luteum adenylate cyclase

The use of a competitive protein-binding assay for cyclic AMP, utilizing the binding protein purified from bovine adrenal cortex, for the study of adenylate cyclase activity of the washed 600 g sediment of bovine corpus luteum is validated. A specific assay for cyclic AMP could only be achieved by removal of the degradation products of ATP on a precipitate of nascent BaSO4. Simple dilution of the sample before assay was not sufficient to eliminate interference from degradation products of ATP. An observed variability in optimal ATP substrate and tissue concentrations is though to reflect variability in the enzymic profile of the cyclic corpus luteum. Optima with respect to F-, Mg2+ and pH are more clearly defined and are similar to those reported for adenylate cyclase systems for other tissues.

Photochemical attachment of cyclic AMP binding protein(s) to the nuclear genome

The nature of the cyclic AMP-receptor-nucleus interactions was examined by a novel combination of two photoreactions. A photosensitive derivative of cyclic AMP, N6-butyryl cyclic AMP, was covalently attached to its cytoplasmic receptod by photo-affinity labelling and this receptor complex was photo-crosslinked by the DNA in the rat liver nuclei. The photolytic reactions seemed to be specific since stable links were formed only when substantial noncovalent binding occured.