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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of the glucitol (gut) operon in Escherichia coli is regulated by an unusual, complex system which consists of an activator (encoded by the gutM gene) and a repressor (encoded by the gutR gene) in addition to the cAMP-CRP complex (CRP, cAMP receptor protein). The activator and repressor are predicted to possess 119 (Mr = 12,955) and 257 (Mr = 28,240) aminoacyl residues, respectively, as deduced from the nucleotide sequences of their structural genes. Both of the genes encoding the two regulators are located downstream from the other known gut structural genes. Reverse transcriptase mapping revealed that the gutM gene is a promoter-distal constituent of the gut operon. The gutR gene has its own promoter, but expression of this gene is primarily due to readthrough from the gut operon operator-promoter. Thus, the gut operon consists of at least five structural genes and has the following gene order: gutOPABDMR. Interestingly, synthesis of the mRNA, which initiates at the promoter specific to the gutR gene, occurs within the gutM gene. Expressional control of the gut operon appears to occur as a consequence of the antagonistic action of the products of the autogenously regulated gutM and gutR genes. An additional cistron of the gut operon, of unknown function, may follow the gutR gene.
J Mol Biol 1988 Oct 05
PMID:Positive and negative regulators for glucitol (gut) operon expression in Escherichia coli. 306 73

Two Escherichia coli control regions have been compared in their ability to be unwound by RNA polymerase during formation of the transcriptionally active ("open") complex: the wild-type control region, consisting of two overlapping binding sites P1 and P2, both weakly transcribed, and an "up" P1 mutant, the strong lac L8UV5 promoter. The final complexes were characterized by their topological unwinding, by DNase I and orthophenanthroline footprints, as well as by methylation of unpaired cytosine residues. At the wild-type control region, the RNA polymerase footprint is weak, and single-strand formation is incomplete and slow. The same signals are strong, complete and quickly established at lac L8UV5; yet the final complexes were found to be equally unwound (by 1.7 turns) in the absence of nucleotide substrates as well as during an abortive initiation cycle. At the lac wild-type region, open complex formation occurs slowly enough to permit the measurement of the extent of a single-stranded region and of topological unwinding during the latency period. Not all the final species are active and unwinding appears to precede, in time, full open-complex formation. At the lac UV5 promoter the same conclusion was reached by a different method involving those changes in the various parameters that characterize open-complex formation monitored by an abortive initiation assay, conducted at increasing levels of template superhelicity. From both approaches we conclude that, at these promoters, the formation of the single-stranded region occurs at the expense of a negative change in linking number, initially stored in a closed intermediate, perhaps as negative writhing. Furthermore, abortive transcription assays indicate that the specific initiation efficiency of the species stored at both promoters, P1 and P2, on the wild-type template is increased as a whole with increasing superhelicity (conversion of inactive species to active ones, increased efficiency of active ones). We conclude that negative supercoiling is not an extra-regulatory element of the lactose system, allowing modulation of expression of the wild-type promoter to the profit of P1. Instead, P2 and P1, in the absence of active catabolite receptor protein (CRP-cAMP), appear to be equally weak and to be equally affected by negative supercoiling in the range of superhelical densities examined. The physiological importance of the P1-P2 competition in the regulation of expression in this region is thus questioned. The major effect of CRP-cAMP stimulation appears to be the direct activation at the P1 promoter.
J Mol Biol 1987 Jun 20
PMID:Topological unwinding of strong and weak promoters by RNA polymerase. A comparison between the lac wild-type and the UV5 sites of Escherichia coli. 330 41

Several strains of Escherichia coli K12 were compared for activity of the periplasmic "pH 2.5 acid phosphatase", an enzyme whose expression is regulated negatively by cyclic AMP. Two distinct enzyme levels differing by about four-fold were observed. This strain-dependent difference does not involve modifications in the structure of the enzyme, but results from a difference in its expression. We show that strains with a high- or a low level of enzyme differ in the gene locus appR located in the 59 min region of the chromosome, a site remote from the structural gene appA; the appR+ versus appR enzyme ratio is 3-4 in wild-type strains, adenylate cyclase-deficient strains (cya) or cyclic AMP receptor protein-deficient strains (crp) grown in rich medium or in glucose minimal medium, but is close to 1 in cya strains in the presence of 0.1 mM cyclic AMP and in wild-type strains grown with succinate as carbon source; in a crp genetic background, appR strains, contrary to appR+ strains, are able to grow on minimal medium with succinate as the sole carbon source. The selection, from an appR+ crp strain, of clones growing on succinate-minimal medium, yielded mutations in the same region of the chromosome and showing the same phenotype as "naturally-occurring" appR strains. All appR strains analysed so far showed other similar deficiencies. The possibility that mutated appR gene products might function as weak substitutes for a functional cAMP-CRP complex is discussed.
Mol Gen Genet 1986 Feb
PMID:Pleiotropic mutations in appR reduce pH 2.5 acid phosphatase expression and restore succinate utilisation in CRP-deficient strains of Escherichia coli. 351 93

CRP-cAMP was shown to activate transcription initiation at the Escherichia coli lac promoter in vitro as a result of two separate effects. An indirect component of the activation resulted from an enhancement of the fraction of promoters productively bound by RNA polymerase. This effect was due largely to CRP-cAMP repression of RNA polymerase binding to an overlapping site (lac P2) within the promoter region. In addition, a direct enhancement of RNA polymerase binding at the principal lac promoter (lac P1) was found. The combination of indirect and direct activation by CRP-cAMP was suggested to be responsible for the large activation observed in vivo. Promoter strength parameters were also determined for the L8, UV5 and Ps promoters. The effect of CRP-cAMP on these mutant promoters was shown to be consistent with the activation mechanism deduced for the lac wild-type promoter. DNA supercoiling enhanced the promoter strength of the lac wild-type and UV5 promoters. The combination of supercoiling and CRP-cAMP was necessary for optimal promoter strength for the lac wild-type promoter.
J Mol Biol 1984 Dec 25
PMID:Mechanism of CRP-cAMP activation of lac operon transcription initiation activation of the P1 promoter. 609 91

Three out of four anti-C-reactive protein monoclonal antibodies [HB3-2, (micro, k)], EA4-1 (gamma 2a, k) and FB2-1 (gamma 1, k) bind to C-reactive protein in the presence of 2.5 mM Ca2+ but not in the presence of 1.0 mM EDTA, indicating that the conformation of the antigenic determinant(s) recognized by these three antibodies is dependent upon Ca2+. This Ca2+-dependent binding can be inhibited by 1.0 mM phosphocholine, indicating that this antigenic determinant is at or near the phosphocholine-binding site of C-reactive protein. The binding of the fourth monoclonal antibody [HD2-4 (gamma 2-k)] is independent of the presence of Ca2+ and is not inhibited by phosphocholine. HB3-2 (micro, k) recognizes an antigenic determinant on the structurally related proteins, rabbit CRP and serum amyloid P.
Mol Immunol 1982 Sep
PMID:Demonstration of calcium-induced conformational change(s) in C-reactive protein by using monoclonal antibodies. 618 79

The regulatory protein CRP (or CAP) from E. coli is shown to display two distinct patterns of binding interactions with DNA-dependent RNA polymerase. The free core enzyme, and both the core and the holo polymerase when bound to single-stranded DNA, can bind CRP in a cAMP-independent association reaction. Instead, the binding of CRP to free holoenzyme and to holo or core polymerase bound to native DNA was undetectable in the absence of cAMP. The specific ligand of CRP (cAMP) strengthens distinctively this class of interactions. In no case could any release of sigma-factor be demonstrated. Estimates of the dissociation constants were obtained for the various binding reactions which were investigated under quasi-physiological ionic conditions. These, together with the known values of the in vivo concentrations of CRP and RNA polymerase, suggest that the interactions described may have a functional significance.
Mol Biol Rep 1980 Mar 31
PMID:Binding of CRP to DNA-dependent RNA polymerase from E. coli: modulation by cAMP of the interactions with free and DNA-bound holo and core enzyme. 624 68

The synthesis of the adenylate cyclase [ATP pyrophosphatelyase-(cyclizing), E.C. 4.6.1.1.] of Escherichia coli, appears to be regulated negatively by the cAMP receptor protein, CRP. This conclusion is based on a comparison of adenylate cyclase activities measured in vitro with the rates of cAMP synthesis by intact bacteria. The activity of adenylate cyclase, depending on conditions of growth, is also regulated by CRP; this effect, however, is indirect insofar as it is mediated by a protein or proteins under CRP control.
Mol Gen Genet 1981
PMID:Regulation of the synthesis of adenylate cyclase in Escherichia coli by the cAMP -- cAMP receptor protein complex. 626 21

The preincubation of a DNA with E. coli RNA polymerase provides its partial protection against the HindII, BspRI and AluI cleavage giving possibility to determine the location of RNA polymerase tight-binding sites. Using this approach about 16 RNA polymerase tight-binding sites were detected on replicative form of phiX174 phage DNA. The protection degree of each of these sites depended on the preincubation conditions. Some of the protected sites hit the known phiX174 promoters and rho-dependent terminators and the other were distributed along the whole phiX174 DNA molecule. Many of them could be considered as potential promoters because they contain all the necessary elements specifying the real promoter sequences. At least some of the intrinsic promoter elements could be observed next to the rest of protected sites. One of the protected sites (R6b/l) is located in phiX174 DNA region which is very similar to the cAMP-CRP-controlled promoter sequences. It was confirmed that phiX174 DNA has two B promoters positioned by Sanger on the phiX174 nucleotide map, according to our data obtained by RNA polymerase protection experiments along with RNA product analysis of the R8 DNA fragment transcription in vitro.
Mol Biol (Mosk)
PMID:[Protection of segments of replicative form I of phiX174 phage DNA recognized by HindII, BspRI, and AluI restrictases by Escherichia coli RNA-polymerase]. 627 99

Mutations in the pts genes (which code for the enzyme I and HPr protein - the general components of the phosphoenolypyruvate-dependent phosphotransferase system) lead to decreases in enzyme-inducible synthesis at the level of transcription. The intracellular content of cyclic AMP in the ptsIH mutant was severely diminished, while the ptsH bacteria contain the same amounts of this nucleotide as the wild-type cells. Nevertheless expression of the lac operon was diminished in the ptsH as well as in the ptsIH mutant. The exogenous cyclic AMP did not prevent repression of beta-galactosidase synthesis in a delta cya ptsI mutant in a wide range of concentrations in the growth medium (from 0.05 mM to 5 mM). The combination of ptsI or ptsH mutations with rpoC1 (synthesis of thermosensitive beta' subunit of RNA polymerase) leads to greater disturbance of beta-galactosidase production at the nonpermissive temperature than demonstrated in the pts+ rpoC1 strain. The stimulatory effect of exogenous cyclic AMP was more pronounced in pts rpoC1 than in pts+ rpoC1 bacteria. The data presented confirm the hypothesis that pts mutations alter the function of CRP in initiation of transcription.
Mol Gen Genet 1983
PMID:Effect of ptsI and ptsH mutations on initiation of transcription of the Escherichia coli lactose operon. 630 97

The non-specific DNA binding of CRP and its N-terminal core, alpha CRP, to a 298 base pair DNA fragment, in the presence and absence of cAMP, has been studied using the nitrocellulose filter binding technique and analysed quantitatively using the theory of Clore et al. [J. Mol. Biol. (1982) 155, 447-466]. It is shown that both CRP and alpha CRP bind cooperatively to DNA. At an ionic strength of 100 mM and pH 7.5, the intrinsic equilibrium association constant for the binding of alpha CRP to DNA is approximately 10-times smaller than that for CRP, but the cooperativity parameter is approximately 17-times larger for alpha CRP than CRP. cAMP exerts its effect solely on the intrinsic equilibrium constant and does not alter the cooperativity. In the case of alpha CRP, cAMP reduces the intrinsic equilibrium association constant by a factor of 3, in contrast to the case of CRP where cAMP increases it by a factor of 3. The possible location of the DNA binding site present in the N-terminal core of CRP is discussed in the light of crystallographic data on the cAMP . CRP complex [McKay et al. (1982) J. Biol. Chem. 257, 9518-9524].
 ...
PMID:Cooperative non-specific DNA binding of the N-terminal core of the cyclic AMP receptor protein of Escherichia coli and its modulation by cyclic AMP. 631 44


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