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PubMed2004

The Lactobacillus casei ptsHI47T mutation causes overexpression of a LevR-regulated but RpoN-independent operon encoding a mannose class phosphotransferase system.

A proteome analysis of Lactobacillus casei mutants that are affected in carbon catabolite repression revealed that a 15-kDa protein was strongly overproduced in a ptsHI47T mutant. This protein was identified as EIIA of a mannose class phosphotransferase system (PTS). A 7.1-kb DNA fragment containing the EIIA-encoding open reading frame and five other genes was sequenced. The first gene encodes a protein resembling the RpoN (sigma54)-dependent Bacillus subtilis transcription activator LevR. The following pentacistronic operon is oriented in the opposite direction and encodes four proteins with strong similarity to the proteins of the B. subtilis Lev-PTS and one protein of unknown function. The genes present on the 7.1-kb DNA fragment were therefore called levR and levABCDX. The levABCDX operon was induced by fructose and mannose. No "-12, -24" promoter typical of RpoN-dependent genes precedes the L. casei lev operon, and its expression was therefore RpoN independent but required LevR. Phosphorylation of LevR by P approximately His-HPr stimulates its activity, while phosphorylation by P approximately EIIBLev inhibits it. Disruption of the EIIBLev-encoding levB gene therefore led to strong constitutive expression of the lev operon, which was weaker in a strain carrying a ptsI mutation preventing phosphorylation by both P approximately EIIBLev and P approximately His-HPr. Expression of the L. casei lev operon is also subject to P-Ser-HPr-mediated catabolite repression. The observed slow phosphoenolpyruvate- and ATP-dependent phosphorylation of HPrI47T as well as the slow phosphoryl group transfer from the mutant P approximately His-HPr to EIIALev are assumed to be responsible for the elevated expression of the lev operon in the ptsHI47T mutant.

Amino Acid Sequence↗

PubMed2005

Characterization of PmfR, the transcriptional activator of the pAO1-borne purU-mabO-folD operon of Arthrobacter nicotinovorans.

Nicotine catabolism by Arthrobacter nicotinovorans is linked to the presence of the megaplasmid pAO1. Genes involved in this catabolic pathway are arranged on the plasmid into gene modules according to function. During nicotine degradation gamma-N-methylaminobutyrate is formed from the pyrrolidine ring of nicotine. Analysis of the pAO1 open reading frames (ORF) resulted in identification of the gene encoding a demethylating gamma-N-methylaminobutyrate oxidase (mabO). This gene was shown to form an operon with purU- and folD-like genes. Only in bacteria grown in the presence of nicotine could transcripts of the purU-mabO-folD operon be detected, demonstrating that this operon constitutes part of the pAO1 nicotine regulon. Its transcriptional start site was determined by primer extension analysis. Transcription of the operon was shown to be controlled by a new transcriptional regulator, PmfR, the product of a gene that is transcribed divergently from the purU, mabO, and folD genes. PmfR was purified, and electromobility shift assays and DNase I-nuclease digestion experiments were used to determine that its DNA binding site is located between -48 and -88 nucleotides upstream of the transcriptional start site of the operon. Disruption of pmfR by homologous recombination with a chloramphenicol resistance cassette demonstrated that PmfR acts in vivo as a transcriptional activator. Mutagenesis of the PmfR target DNA suggested that the sequence GTTT-14 bp-AAAC is the core binding site of the regulator upstream of the -35 promoter region of the purU-mabO-folD operon.

Amino Acid Sequence↗

PubMed2005

Characterization of copABCD operon from a copper-sensitive Pseudomonas putida strain.

We describe an operon, copABCD, that encodes copper-binding and sequestering proteins for copper homeostasis in the copper-sensitive strain Pseudomonas putida PNL-MK25. This is the second operon characterized as being involved in copper homeostasis, in addition to a P1-type ATPase encoded by cueAR, which was previously shown to be active in the same strain. In this study, 3 copper-responsive mutants were obtained through mini-Tn5::gfp mutagenesis and were found to exhibit reduced tolerance to copper. Sequencing analysis of the transposon-tagged region in the 3 mutants revealed insertions in 2 genes of an operon homologous to the copABCD of P. syringae and pcoABCD of Escherichia coli. Gene expression studies demonstrated that the P. putida copABCD is inducible starting from 3 micromol/L copper levels. Copper-sensitivity studies revealed that the tolerance of the mutant strains was reduced only marginally (only 0.16-fold) in comparison to a 6-fold reduced tolerance of the cueAR mutant. Thus, the cop operon in this strain has a minimal role when compared with its role both in other copper-resistant strains, such as P. syringae pv. syringae, and in the cueAR operon of the same strain. We propose that the reduced function of the copABCD operon is likely to be due to the presence of fewer metal-binding domains in the encoded proteins.

Amino Acid Sequence↗

PubMed2006

Operon information improves gene expression estimation for cDNA microarrays.

BACKGROUND: In prokaryotic genomes, genes are organized in operons, and the genes within an operon tend to have similar levels of expression. Because of co-transcription of genes within an operon, borrowing information from other genes within the same operon can improve the estimation of relative transcript levels; the estimation of relative levels of transcript abundances is one of the most challenging tasks in experimental genomics due to the high noise level in microarray data. Therefore, techniques that can improve such estimations, and moreover are based on sound biological premises, are expected to benefit the field of microarray data analysis RESULTS: In this paper, we propose a hierarchical Bayesian model, which relies on borrowing information from other genes within the same operon, to improve the estimation of gene expression levels and, hence, the detection of differentially expressed genes. The simulation studies and the analysis of experiential data demonstrated that the proposed method outperformed other techniques that are routinely used to estimate transcript levels and detect differentially expressed genes, including the sample mean and SAM t statistics. The improvement became more significant as the noise level in microarray data increases. CONCLUSION: By borrowing information about transcriptional activity of genes within classified operons, we improved the estimation of gene expression levels and the detection of differentially expressed genes.

Animals↗

PubMed1992

Structure and regulation of the glpFK operon encoding glycerol diffusion facilitator and glycerol kinase of Escherichia coli K-12.

The glpFK operon maps near minute 88 on the linkage map of Escherichia coli K-12 with glpF promoter proximal. The glpF gene encodes a cytoplasmic membrane protein which facilitates the diffusion of glycerol into the cell. The glpK gene encodes glycerol kinase. In the present work, the nucleotide sequence of the 5'-end of the operon, including the control region, the glpF gene, and part of the glpK gene, was determined. The facilitator was predicted to contain 281 amino acids with a calculated molecular weight of 29,780. It is a highly hydrophobic protein with a minimum of six potential transmembrane alpha helices. The transcription start site for the glpFK operon was located 71 base pairs upstream from the proposed translation start codon for glpF. Preceding the transcription start site were sequences similar to the -10 and -35 consensus sequences for bacterial promoters. Binding sites for the cAMP-cAMP receptor protein (CRP) complex and the glp repressor were identified by DNase I footprinting. The region protected by the cAMP.CRP complex contained tandem sequences resembling the consensus sequence for CRP binding. The CRP sites were centered at 37.5 and 60.5 base pairs upstream of the start of transcription. The glp repressor protected an extensive area (-89 to -7 relative to the start point of transcription), sufficient for the binding of four repressor tetramers. Two additional binding sites for the repressor were identified within the glpK coding region. The DNA containing these two operators synergistically increased the apparent affinity of glp repressor for DNA fragments containing the four operators in the promoter region of the glpFK operon. With this study, a total of 13 operators for the glp regulon have been characterized. Comparison of these operators revealed the consensus 5'-WATGTTCGWT-3' for the operator half-site (W = A or T). The relative affinity of the glp repressor for the various glp operators was assessed in vivo using a promoter-probe vector. The relative apparent affinity of the control regions for glp repressor was glpFK greater than glpD greater than glpACB greater than glpTQ. The degree of catabolite repression for each of the operons was assessed using a similar system. In this case, the relative sensitivity of the glp operons to catabolite repression was glpTQ greater than glpFK greater than glpACB greater than glpD.

Amino Acid Sequence↗

PubMed1992

Characterization of the tryptophanase operon of Proteus vulgaris. Cloning, nucleotide sequence, amino acid homology, and in vitro synthesis of the leader peptide and regulatory analysis.

The tryptophanase (tna) operon of Proteus vulgaris was cloned and characterized and found to be organized similarly to the tna operon of Escherichia coli. Both operons contain two major structural genes, tnaA and tnaB, that encode tryptophanase and a tryptophan permease, respectively. tnaA of P. vulgaris is preceded by a transcribed leader region, encoding a 34-residue leader peptide, TnaC, that contains a single tryptophan residue. The tnaC coding region also has a boxA-like sequence. Regulatory studies performed in P. vulgaris, and with a plasmid carrying the P. vulgaris tna operon in E. coli, established that expression of the Proteus operon was induced by tryptophan and was subject to catabolite repression. Site-directed mutagenesis studies established that translation of the tnaC coding region was essential for induction. Synthesis of the P. vulgaris leader peptide was demonstrated in an in vitro coupled transcription-translation system. Interestingly, the 5 amino acid residues of the TnaC peptide surrounding the sole tryptophan residue are identical in P. vulgaris and E. coli. We conclude that the tna operon of P. vulgaris is also regulated by tryptophan-induced transcription antitermination. Homology of tryptophanase and tryptophan permease of P. vulgaris to related proteins from other species is described.

Amino Acid Sequence↗

PubMed1992

Interaction at a distance between multiple operators controls the adjacent, divergently transcribed glpTQ-glpACB operons of Escherichia coli K-12.

The glp regulon of Escherichia coli encodes the proteins required for utilization of sn-glycerol 3-phosphate and its precursors. Transcription of the divergently transcribed glpTQ and glpACB operons is initiated at sites separated by 132 base pairs (bp) of DNA. These operons are controlled negatively by glp repressor and positively by the cAMP-cAMP receptor protein (CRP) complex. The locations of the binding sites for the glp repressor and for cAMP.CRP in the control regions of these operons were determined by DNase I footprinting. Binding of the glp repressor protected the region -32 to -51 (OT) in the glpTQ promoter, which was also the binding site for cAMP.CRP. Four repressor binding sites (-41 to -60 (OA1), -9 to -28 (OA2), +12 to -8 (OA3), and +52 to +33 (OA4)) and two cAMP.CRP binding sites (+11 to -11 and -30 to -51) were found in the glpACB promoter region. Comparison of the sequences of the repressor binding sites found in the glpTQ-glpACB control region with those operators previously described in the glpD operon allowed formulation of a consensus operator sequence which was the palindrome 5'-WATGTTCGWTAWC-GAACATW-3' (W is A or T). The role of each operator was assessed by measuring repression in constructs where individual operators were altered by site-directed mutagenesis. Alteration of OT did not significantly decrease repression of either operon. Each of the glpACB operators contributed to repression of both operons. These results suggest involvement of glpACB operator(s) in control of glpTQ expression perhaps via formation of a repression loop. Evidence supporting this hypothesis was obtained by measuring the degree of repression of the glpTQ promoter in constructs containing 6- or 10-bp insertions between the glpTQ and glpACB operators. A 6-bp insertion located within OA2 or between OT and OA1 eliminated repression of the glpTQ promoter, whereas significant repression was maintained in the case of a 10-bp insertion within OA2.

Base Sequence↗

PubMed1991

RNA polymerase activity may regulate transcription initiation and attenuation in the rplKAJLrpoBC operon in Escherichia coli.

The relationship between global RNA transcription capacity and transcript initiation, attenuation, and stability in the rplKAJLrpoBC operon of Escherichia coli has been examined. The rplKAJLrpoBC operon encodes in order the four large ribosome subunit proteins, L11, L1, L10, and L12, and the two large beta and beta' subunits of RNA polymerase. Operon transcripts are initiated at two promoters, PL11 and PL10. The L12-beta intergenic space contains a transcription attenuator which, during balanced growth, terminates about 80% of the transcripts exiting the L12 gene; the remaining transcripts read through into the beta and beta' encoding genes. The capacity for global transcription initiation was modulated using a strain carrying a temperature-sensitive, initiation-defective mutation in rpoC. Following a shift to 39 degrees C, the global transcription initiation capacity was reduced to about one-half the level at 30 degrees C. This partial restriction resulted in a decrease in the stability of distal beta mRNA, whereas the stability of proximal L11-L1 and L10-L12 mRNA was not changed. Measurements of the synthesis rates of L11-L1, L10-L12, and beta mRNAs relative to total RNA synthesis indicated that this operon was selectively transcribed when the initiation capacity of RNA polymerase was limited. The synthesis rates of L11-L1 and L10-L12 mRNA increased about 2-fold, whereas the synthesis rate of beta mRNA increased nearly 5-fold. The relative transcription of other ribosome component genes and the alpha subunit gene exhibited only a modest increase during the partial restriction. Protection from S1 nuclease was used to demonstrate that the preferential transcription within the operon of beta mRNA was the consequence of active regulation of termination-antitermination at the attenuator structure in the L12-beta intergenic space. These results demonstrate that global transcription capacity may be an important parameter in determining both initiation and attenuation of transcription of the rplKAJLrpoBC ribosomal protein-RNA polymerase operon.

Base Sequence↗

PubMed1990

Structure of an ATPase operon of an acidothermophilic archaebacterium, Sulfolobus acidocaldarius.

The nucleotide sequence of the operon of the ATPase complex of an acidothermophilic archaebacterium, Sulfolobus acidocaldarius, has been determined. In addition to the three previously reported genes for the alpha, beta, and c (proteolipid) subunits of the ATPase complex (Denda, K., Konishi, J., Oshima, T., Date, T., and Yoshida, M. (1989) J. Biol. Chem. 264, 7119-7121), the operon contained three other genes encoding hydrophilic proteins with molecular masses 25, 13, and 7 kDa. The 25-kDa protein is the third largest subunit (gamma), the 13-kDa protein is most likely the fourth subunit (delta), and the 7-kDa protein may correspond to an unknown subunit of the ATPase, tentatively named as epsilon subunit. They do not have significant sequence similarity to subunits in F0F1-ATPases and eukaryotic V-type ATPases, whereas the other three subunits, alpha, beta, and c, have homologous counterparts in F0F1- and V-type ATPases. The order of the genes in the operon was delta alpha beta gamma epsilon c. The S. acidocaldarius ATPase operon differed from the eucabacterial F0F1-ATPase operon in that the former contains only one gene for a hydrophobic subunit at the most downstream part of the operon whereas the latter has three hydrophobic F0 genes preceding five hydrophilic F1 genes.

Adenosine Triphosphatases↗

PubMed1990

[The effect of specific mutation crp a in the genetic locus of receptor protein cAMP (CRP) on the expression of Escherichia coli K-12 deo-operon].

Expression of the deo operon of Escherichia coli is subjected to double negative control by DeoR and CytR repressors and to the positive control by cAMP-CRP complex. However, sensitivity of the deo operon to catabolite repression is only revealed in bacteria with disrupted synthesis of the CytR protein, since the function of the latter is to prevent CRP activation of the deo operon transcription. In the present work we have studied the influence of crpa specific mutation at the genetic locus of CRP protein on the expression of the deo operon of E. coli. It has been found that the presence of crpa mutation in bacterial genome completely eliminates CytR repression of the deo operon, so that activation of Deo enzymes synthesis by cAMP-CRPa complex becomes possible, even in the presence of CytR. Besides, the modified CRPa protein appears to block the activity of catabolite-sensitive deoPO2 promoter of the deo operon under conditions of cAMP deficiency, which is manifested in the two-fold decrease of deoR derepression in the crpa cells, as compared to the wild type bacteria during the growth on glucose containing medium. It has been supposed that both effects are due to increased affinity of the modified CRPa protein to the specific sites of catabolite sensitive promoters, as compared to the wild type CRP protein.

Escherichia coli↗

PubMed1987

Transcription control elements of the Mycoplasma pneumoniae rRNA operon.

The single RNA operon of Mycoplasma pneumoniae was cloned into a lambda vector and subcloned into pBR322. This was carried out in order to enable the analysis of the transcription control regions of this operon. S1 nuclease mapping was used to locate the 5' ends of RNA transcripts synthesized from the operon. The 5' ends of the 23S, 16S, and a precursor RNA synthesized in vivo in M. pneumoniae were mapped on the DNA template. Preliminary in vitro transcription experiments using RNA polymerase of Escherichia coli led to the conclusion that E. coli recognizes one promoter in the 5' region of the M. pneumoniae rRNA operon. The startsite of the in vitro transcript seems to lie downstream from the 5' end of the M. pneumoniae precursor transcript. Preliminary sequencing of the 5' regions of the M. pneumoniae rRNA operon and of the M. capricolum rRNA B operon enabled their comparison to each other and to known sequences from other organisms.

DNA, Bacterial↗

PubMed1989

Nitrogen fixation (nif) genes of the cyanobacterium Anabaena species strain PCC 7120. The nifB-fdxN-nifS-nifU operon.

A second nitrogen fixation (nif) operon in the cyanobacterium (blue-green alga) Anabaena (Nostoc) sp. strain PCC 7120 has been identified and sequenced. It is located just upstream of the nifHDK operon and consists of four genes in the order nifB, fdxN, nifS, and nifU. The three nif genes were identified on the basis of their similarity with the corresponding genes from other diazotrophs. The fourth gene, fdxN, codes for a bacterial type ferredoxin (Mulligan, M. E., Buikema, W. J., and Haselkorn, R. (1988) J. Bacteriol. 167, 4406-4410). The four genes are probably transcribed as a single operon, but are expressed at a lower level than the nifHDK operon, and only after a developmentally induced DNA rearrangement occurs that excises a 55-kilobase pair element from within the fdxN gene (Golden, J. W., Mulligan, M. E., and Haselkorn, R. (1987) Nature 327, 526-529; Golden, J. W., Carrasco, C. D., Mulligan, M. E., Schneider, G. J., and Haselkorn, R. (1988) J. Bacteriol. 170, 5034-5041). The promoter for the nifB operon was located by primer extension. Comparison of the nifB 5'-flanking sequence with the nifH 5'-flanking sequence did not reveal any consensus base pairs that would define a nif promoter for Anabaena. The operon contains two instances of 7-base pair directly repeated sequences: seven copies of the repeated sequence are found between the nifB and fdxN genes and six copies are found between the nifS and nifU genes. The function of these repeats is unknown.

Amino Acid Sequence↗

PubMed1989

Transcriptional analysis of puf operon expression in Rhodobacter sphaeroides 2.4.1 and an intercistronic transcription terminator mutant.

DNA sequence analysis of the pufX region, the most distal gene of the pufBALMX operon of Rhodobacter sphaeroides, revealed a sequence encoding a putative polypeptide of 82 amino acids with a molecular mass of 9052 Da followed by a puf operon-specific transcription terminator. Analysis of the 5' and 3' termini of the transcripts produced in vivo from the puf operon of R. sphaeroides PUF delta 348-420 (three transcripts; 0.59, 0.64, and 2.63 kilobases) lacking the puf-intercistronic terminator structure were identical to those of the corresponding puf transcripts derived from wild-type R. sphaeroides 2.4.1 (four transcripts; 0.50, 0.66, 0.71, and 2.7 kilobases) showing that the transcripts begin and end at the same sites. However, the absence of the puf intercistronic terminator resulted in both the loss of the smallest transcript found in wild type and increased transcriptional read-through of the mutated region to the more distal pufL gene, supporting our previous contention that the proximal intercistronic stem-loop functions as a transcription terminator. The 5' terminus of the medium sized puf transcript has been localized to the same site as that of the small puf transcript. These analyses also showed conclusively that the puf operon-specific transcripts are not extended transcripts derived from the upstream open reading frame Q. In addition, a 120-nucleotide RNA was detected which encompassed the terminator region downstream of pufX and extended into the next downstream open reading frame. The 120-nucleotide RNA of unknown function was regulated by O2 and is unique in its abundance and stability. By comparison with strain 2.4.1, the mutant PUF delta 348-420 showed an increased amount (1.9-fold) of the 120-nucleotide RNA, suggesting that its synthesis is under the control of the puf operon despite the fact that its sequence appears to overlap the next downstream operon.

Amino Acid Sequence↗

PubMed1995

Metabolic operons in Lactococci.

The genes for the biosynthesis of histidine, tryptophan and branched-chain amino acids (ilv for isoleucine, leucine and valine) are clustered in large operons. In addition to genes encoding the pathway enzymes, the his and the ilv operons contain 4 and 3 other genes, respectively. The functions of two of these, orf3 and aldB are regulatory. The second gene of the his operon, orf3, encodes a protein homologous to the histidyl-tRNA synthetases. It is involved in transcription attenuation upstream of the his operon. This regulation is related to a new class of attenuation mechanisms controlling the expression of most tRNA synthetase genes and a few metabolic operons in Gram-positive bacteria. Gene aldB, the penultimate gene of the ilv operon, encodes acetolactate decarboxylase. This enzyme transforms acetolactate (AL), the first intermediate of leucine and valine biosynthesis, into acetoin. AL decarboxylase is positively controlled by the availability of leucine and possibly valine in the cell. This is the key enzyme for a new class of regulatory mechanisms, a metabolic shunt which guides the AL flux towards synthesis of amino acids or a secondary metabolite.

Amino Acid Sequence↗

PubMed1995

Analysis of the genes forming the distal parts of the two cbb CO2 fixation operons from Alcaligenes eutrophus.

In the facultative chemoautotroph Alcaligenes eutrophus H16, most of the genes (cbb genes) encoding enzymes of the Calvin carbon reduction cycle are organized within two highly homologous cbb operons, one located on the chromosome and the other on the megaplasmid pHG1. Nucleotide sequencing of the promoter-distal part of the operons revealed three open reading frames, designated cbbG, cbbK, and cbbA. Similarity searches in databases and heterologous expressions of the subcloned genes in Escherichia coli identified them as genes encoding the Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase, 3-phosphoglycerate kinase, and a class II fructose-1,6-bisphosphate aldolase, respectively. The aldolase could be grouped together with the enzymes from Rhodobacter sphaeroides and Bacillus subtilis as a new subtype of class II aldolases. A phenotypic complementation analysis with a cbb operon mutant of A. eutrophus showed that the cbbG product is essential for autotrophic growth of the organism, whereas the products of cbbK and cbbA can apparently be substituted by isoenzymes encoded elsewhere on the chromosome. No or only low constitutive promoter activity was associated with cbbK and cbbA, respectively, confirming the two genes as parts of the cbb operon. Downstream of cbbA, the very high overall nucleotide sequence identity (about 94%) prevailing throughout the two cbb operons discontinues, suggesting that cbbA is the most promoter-distal gene of the operon.

Alcaligenes↗

PubMed1995

Analysis of an insertional operator mutation (gntOi) that affects the expression level of the Bacillus subtilis gnt operon, and characterization of gntOi suppressor mutations.

The Bacillus subtilis gnt operon is negatively regulated via interaction of the gnt repressor (GntR) with an operator upstream of gntR, which is antagonized by gluconate. An 8 bp insertional operator mutation (gntOi) of the gnt operon was constructed which affected the expression level of this operon. Two suppressors of this gntOi mutation, exhibiting normal expression, were also isolated; one involved a threonine substitution for the Ala-48 residue (gntR48T) within the helix-turn-helix DNA-binding motif of GntR, and the other an adenine substitution for the guanine at nucleotide -4 within the gntOi operator (gntOiM4A) (+ 1 is the transcription initiation site). The gntR48T mutation by itself rendered the gnt operon partially constitutive. When the gntR43L mutation, which renders the gnt operon fully constitutive, was introduced into the gntOi or gntOiM4A mutant, the operator mutations were found not to affect the promoter activity of the gnt operon. These in vivo results indicate that the gntOi mutation affects the operator interaction with GntR, causing a low expression level even in the presence of gluconate. In vitro gel retardation and DNase I footprint analyses demonstrated that even when gluconate was present, GntR still bound to the gntOi operator region.

Amino Acid Sequence↗

PubMed1998

Molecular characterization of the operon comprising the spoIV gene of Bacillus megaterium DSM319 and generation of a deletion mutant.

According to sequence analysis, the spoIV-locus of Bacillus megaterium DSM 319 is 1,185 bp long; it is the second gene of a sporulation operon, which altogether contains three open reading frames. The ORF preceding spoIV encodes a putative polypeptide with 94 amino acids; the 3rd ORF of the operon has 972 bp corresponding to 324 amino acids. The operon is flanked on both sides by palindromic sequences, probably representing Rho-independent terminators. A primer extension analysis revealed that mRNA synthesis starts immediately downstream of a promoter, which is similar to the consensus sequence of Bacillus subtilis sigma(E) dependent promoters. Both the -35 and the -10 region are within the terminator region of the preceding operon. Gene knockout experiments and reporter gene assays with a newly developed system based on the heterologous Paenibacillus macerans glucanase gene (bgl) confirmed sigma(E)-dependent transcription. Two open reading frames of a further upstream operon were also identified. Northern analysis revealed that transcription of these ORFs comes about in late sporulation phases. The genetic organization of the spoIV comprising operon and adjacent loci clearly resembles that of the B. subtilis yqfa-phoH gene cluster. Thus our findings are of general significance for endospore-forming bacteria.

Journal Article↗

PubMed1977

[Functioning of the lactose operon of E. coli K-12 under the influence of non-specific regulators].

A possible role played by cAMP in the stimulating action of ACTH and hydrocortisone on lactose E. coli K-12 operon was studied. It was shown that ACTH caused no effect in the E. coli WZ-78/F'lac (cya855) and E. coli CA8001 (L1) strains with destroyed positive cAMP control system of the lactose operon function, at the same time producing a stimulating effect on the lactose operon in the strains of wild type, i.e. E coli 200PS/F'lac and E. coli 3000. Hydrocortisone stimulated the lactose operon function both in E. coli 3000 and in the mutant E. coli CA8001 (L1). It was supposed that the accelerating effect of ACTH on the lactose operon was mediated through cAMP; as to hydrocortisone--it stimulated the lactose operon function independently of cAMP.

Adrenocorticotropic Hormone↗