A regulator gene that is dominant on an episome and recessive on a chromosome

Linkage map of Escherichia coli K-12, edition 10: the traditional map

This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.

Escherichia coli carbamoyl-phosphate synthetase: domains of glutaminase and synthetase subunit interaction

Three catalytic domains of the Escherichia coli carbamoyl-phosphate synthetase (EC 6.3.5.5) have been identified in previous studies. These include the glutamine amide-N transfer domain in the carboxyl-terminal half of the glutaminase component and at least two adenine nucleotide binding sites in the synthetase component. To delineate the domains involved in subunit interactions, we have examined the effects of deletions and point mutations in the glutaminase and synthetase subunits on formation of the alpha beta holoenzyme. Deletion of the amino-terminal third of the glutaminase subunit abolishes interactions with the synthetase subunit, suggesting that this domain functions to stabilize the complex. Two subunit binding domains have been identified in the synthetase subunit. They are homologous to one another and are located in the amino-terminal and central regions of the synthetase component. These domains are adjacent to regions of the synthetase previously proposed to be involved in ATP binding and, possibly, activation of CO2. The new data enlarge the definition of the structural and functional domains in the two interdependent components of carbamoyl-phosphate synthetase.

Expression of the polyoma middle-size T antigen in Escherichia coli

We constructed a plasmid encoding a hybrid protein, consisting of the N-terminal signal sequence of the major outer membrane lipoprotein (lpp) of Serratia marcescens joined to the polyoma middle-size T antigen (mT antigen). The hybrid protein expressed under the control of a lpp-lac hybrid promoter was synthesized at levels up to 5% of newly synthesized protein and could be accumulated in Escherichia coli strains carrying the Cap R mutation. The mT antigen produced in E. coli was precipitated by polyoma antitumor serum, and by serum directed against a synthetic peptide corresponding to the C terminus of the authentic mT antigen. The protein was secreted into the periplasmic space, from which it could be released by osmotic shock. The bacterial mT antigen had no detectable associated protein kinase activity.

Regulatory region of the heat shock-inducible capR (lon) gene: DNA and protein sequences

The CapR protein is an ATP hydrolysis-dependent protease as well as a DNA-stimulated ATPase and a nucleic acid-binding protein. The sequences of the 5' end of the capR (lon) gene DNA and N-terminal end of the CapR protein were determined. The sequence of DNA that specifies the N-terminal portion of the CapR protein was identified by comparing the amino acid sequence of the CapR protein with the sequence predicted from the DNA. The DNA and protein sequences established that the mature protein is not processed from a precursor form. No sequence corresponding to an SOS box was found in the 5' sequence of DNA. There were sequences that corresponded to a putative -35 and -10 region for RNA polymerase binding. The capR (lon) gene was recently identified as one of 17 heat shock genes in Escherichia coli that are positively regulated by the product of the htpR gene. A comparison of the 5' DNA region of the capR gene with that of several other heat shock genes revealed possible consensus sequences.

Regulation of cell division in Escherichia coli: SOS induction and cellular location of the sulA protein, a key to lon-associated filamentation and death

Mutations in sulA (sfiA) block the filamentation and death of capR (lon) mutants that occur after treatments that either damage DNA or inhibit DNA replication and thereby induce the SOS response. Previous sulA-lacZ gene fusion studies showed that sulA is transcriptionally regulated by the SOS response system (lexA/recA). SulA protein has been hypothesized to be additionally regulated proteolytically through the capR (lon) protease, i.e., in lon mutants lacking a functional ATP-dependent protease there would be more SulA protein. A hypothesized function for SulA protein is an inhibitor of cell septation. To investigate aspects of this model, we attempted to construct lon, lon sulA, and lon sulB strains containing multicopy plasmids specifying the sulA+ gene. Multicopy sulA+ plasmids could not be established in lon strains because more SulA protein accumulates than in a lon+ strain. When the sulA gene was mutated by a mini Mu transposon the plasmid could be established in the lon strains. In contrast, sulA+ plasmids could be established in lon+, lon sulA, and lon sulB strains. The sulA+ plasmids caused lon sulA and lon sulB cells to exist as filaments without SOS induction and to be sensitive to UV light and nitrofurantoin. Evidence implicated higher basal levels of SulA protein in these lon plasmid sulA+ strains as the cause of filamentation. We confirmed that the SulA protein is an 18-kilodalton polypeptide and demonstrated that it was induced by treatment with nalidixic acid. The SulA protein was rapidly degraded in a lon+ strain, but was comparatively more stable in vivo in a lon sulB mutant. Furthermore, the SulA protein was localized to the membrane by several techniques.

DNA-stimulated ATPase activity on the lon (CapR) protein

The gene product of the pleiotropic lon (also called capR) locus in Escherichia coli, the CapR protein, is an ATP hydrolysis-dependent protease and a nonspecific nucleic acid-binding protein. We demonstrated that it is also a DNA-stimulated adenosine triphosphatase (ATPase). This new activity is distinct from the protease-associated ATPase activity and occurs in the absence of proteolytic substrate. The reaction requires the presence of a divalent cation and has a pH optimum of 8.0. The products of the reaction are ADP and inorganic phosphate. No adenylation or phosphorylation of the DNA or proteins was detected. The maximum rate of ATP hydrolysis occurs in the presence of supercoiled (form I) DNA. Relaxed circles (form II), double-stranded DNA, and single-stranded DNA are less effective in promoting ATPase activity, whereas RNA is inactive. The DNA-stimulated ATPase activity is inhibited by a mutationally altered form of the CapR protein called the CapR9 protein. The interaction of the CapR and CapR9 subunits suggests that this enzymatic activity of the CapR protein is oligomeric in the presence of DNA. Our in vitro experiments indicate a possible role for nucleic acids in the regulation of all lon (capR) activity.

Overlapping and separate controls on the phosphate regulon in Escherichia coli K12

The physiological and genetic controls operating on phosphate-regulated promoters were studied in greater detail. This was done by defining the control for three phosphate-regulated genes: phoA, psiE, and psiO. Each is highly inducible by phosphate starvation. Individually, these phosphate-starvation-inducible, psi, genes at the same time show common and differing features in their molecular control. The phoA gene, encoding alkaline phosphatase, is specifically induced by phosphate starvation. It is negatively controlled by phoR as well as by the phosphate-specific transport (PST) system in Escherichia coli. phoA induction is positively controlled by the phoB, M, and R products; it is unaffected by the cAMP and CAP system. The psiE and psiO genes were studied by using strains with lacZ fused to their respective promoters. psiE-lacZ is induced by phosphate-, carbon- or nitrogen-limited growth. Genetically, psiE-lacZ induction is partially phoB and phoR-dependent. However, its expression is phoM-independent. This implies that phoB/phoR coupled control differs from phoB/phoM coupled control. Repression of psiE-lacZ is substantially altered in only some PST mutants, such as phoT. In addition, psiE-lacZ is negatively controlled by the cAMP and CAP system. psiO-lacZ is induced by phosphate-, carbon- or nitrogen-limited growth or by anaerobiosis. Its expression is unaffected by any pho mutation that has been previously described. A cell density-dependent induction of psiO-lacZ is observed in lon mutants. Also, psiO-lacZ is negatively controlled by the cAMP-CAP system. In summary, these results demonstrate that co-ordinately regulated promoters can have some common regulatory elements while, at the same time, not sharing other controlling factors.

Identification and purification of the Lon+ (capR+) gene product, a DNA-binding protein

The polypeptide product of the lon (capR) gene was identified and partially purified from bacterial strains homozygous for the capR(+) or capR9 (ochre mutation) alleles cloned with pSC101. A 94,000-dalton polypeptide was identified as the lon (capR) gene product. Studies of binding to DNA cellulose columns and nitrocellulose filters indicate that the capR(+) and capR9 proteins bind DNA.

Cloning of gene lon (capR) of Escherichia coli K-12 and identification of polypeptides specified by the cloned deoxyribonucleic acid fragment

A mutation in the lon (capR) gene of Escherichia coli K-12 results in overproduction of capsular polysaccharide and increased sensitivity to ultraviolet and ionizing radiations. The lon (capR) gene deoxyribonucleic acid was cloned from a new F' factor. The new plasmids, designated pBZ201 and pBZ203, (i) contained an additional 8.2-megadalton (Md) EcoRI fragment that had the same mobility as one of the EcoRI fragments of the F', and (ii) conferred repression of capsular polysaccharide synthesis and repression of sensitivity to ultraviolet radiation in a bacterial transformation experiment with capR mutant recipient strains. A capR9 mutant plasmid, pBZ201M9, was also isolated and conferred expression of mucoidy and ultraviolet sensitivity to a capR(+) (lon(+)) strain, indicating that the capR9 allele was dominant. Plasmids pBZ201M80, pBZ201M9-INSA, and pBZ201M9-INSB were characterized by transformation as containing recessive capR mutant alleles. Heteroduplex analyses and agarose gel electrophoresis of restriction endonuclease digests of plasmid DNA preparations revealed that (i) pBZ201M9-INSA and pBZ201M9-INSB each contains a 0.5-Md insertion (probably IS1) in the cloned DNA fragment at the same site, and (ii) pBZ201 and pBZ203, both capR(+) plasmids, contain the same 8.2-Md fragment cloned in opposite orientations with respect to the cloning vehicle, pSC101. Plasmid-specified polypeptides were determined by using strain CSR603 maxicells containing each plasmid. Two new polypeptides were coded by the lon(+) (capR(+)) 8.2-Md DNA fragment: Z1, 94 kilodaltons (94K), and Z2, 67K. The maxicells containing recessive capR mutant plasmids were deficient only in synthesis of the 94K polypeptide, and the dominant (capR9) mutant plasmid specified 5 to 10 times more of the 94K polypeptide than the maxicells containing the capR(+) plasmid. Other data indicated that the capR9-specified "94K polypeptide" was not identical to the capR(+)-specified "94K polypeptide." Thus the altered mutant polypeptide was synthesized in increased quantities, suggesting a defective mode of autogenous regulation for the capR9 polypeptide and effective autogenous regulation of the capR(+) polypeptide.

Outer membrane protein a and other polypeptides regulate capsular polysaccharide synthesis in E. coli K-12

capR (lon) mutants of Escherichia coli K-12 are mucoid on minimal agar because they produce large quantities of capsular polysaccharide. When such mutants are transformed to tetracycline resistance by plasmid pMC44, a hybrid plasmid that contains a 2 megadalton (Mdal) endonuclease EcoR1 fragment of E. coli K-12 DNA joined to the cloning vehicle-pSC101, capsular polysaccharide synthesis is inhibited and the transformed colonies exhibit a non-mucoid phenotype. Re-cloning of the 2 Mdal EcoR1 fragment onto plasmid pHA105, a min-colE1 plasmid, yielded plasmid pFM100 which also inhibited capsular polysaccharide synthesis in the capR mutants. A comparison of the polypeptides specified by both plasmids pFM100 and pMC44 in minicells demonstrated that seven polypeptide bands were specified by the 2 MDal DNA, one of which was previously demonstrated to be outer membrane protein a; also known as 3b or M2 (40 kilodaltons, Kdal). Plasmid mutants no longer repressing capsular polysaccharide synthesis were either unable to specify the 40 Kdal outer membrane protein a or were deficient in synthesis of 25 Kdal and 14.5 Kdal polypeptides specified by the 2 Mdal DNA fragments. Studies with a minicell-producing strain that also contained a capR mutation indicated that the capR gene product regulated processing of at least one normal protein, the precursor of outer membrane protein a.

Neuroactive drugs inhibit trypsin and outer membrane protein processing in Escherichia coli K-12

Previous studies demonstrated that a cloned 2-megadalton (MDal) fragment of Escherichia coli DNA contained the structural gene for major outer membrane protein a (also known as 3b or M2 (40 kDal). The present study demonstrates that M2 is synthesized from a 42-kDal precursor that also is present in the outer membrane. The conversion of the 42-kDal precursor to M2 is inhibited by a number of different local anesthetics (procaine, piperocaine, lidocaine, cocaine), by the neuroactive drug atropine, and by the classical trypsin inhibitors N alpha-tosyllysine chloromethyl ketone (TLCK) and benzamidine. Our kinetic studies demonstrate that the amidase action of pure trypsin is inhibited competitively by the local anesthetics tested (excluding lidocaine) as well as by atropine and neostigmine. A mechanism of action for local anesthetics as well as atropine in E. coli may to be inhibit trypsinlike proteases, in a competitive manner, in the region of the outer membrane. The mechanism of action of these compounds in regulating nerve conduction in man have certain features in common with the mechanism proposed in E. coli.

Deg phenotype of Escherichia coli lon mutants

Deg. one of the Escherichia coli systems for degrading abnormal polypeptides (e.g., nonsense fragments), is also involved in the degradation of some classes of missense proteins. Both missense proteins of beta-galactosidase and temperature-sensitive phage products appear to be degraded by the Deg system. Mutations in the Deg system are indistinguishable from mutations classically called lon or capR; all map near proC, all are mucoid, defective in protein degradation, sensitive to radiomimetic agents, and defective in P1 lysogenization. All are able to propagate temperature-sensitive phage better than lon+ parental strains. Mutations that suppress the radiation sensitivity of these strains (sul) also suppress the P1 lysogenization defect, but do not affect mucoidy or the degradation defect.

Role of a sugar-lipid intermediate in colanic acid synthesis by Escherichia coli

Membrane fractions from a lon strain of Escherichia coli but not a wild-type strain catalyze the incorporation of fucose from guanosine 5'-diphosphate-fucose into a lipid and into polymeric material. Both incorporation reactions specifically require only uridine 5'-diphosphate (UDP)-glucose. The sugar lipid was shown to be an intermediate in the synthesis of the polymer which was related to colanic acid. The sugar lipid had the structure (fucose3, glucose2)-glucose P-P-lipid. Its behavior on column and thin-layer chromatography, the rates of its hydrolysis in acid and base, and the response of its synthesis to inhibitors are all identical to the other sugar-lipid intermediates which have been shown to contain sugars attached to the C55-polyisoprenol, undecaprenol, by a pyrophosphate linkage. The membrane fractions from both the lon strain and the wild-type strain also catalyzed the incorporation of either glucose from UDP-glucose or galactose from UDP-galactose into a lipid fraction which was shown to contain the free sugar attached by a monophosphate linkage to an undecaprenol-like lipid. This lipid was isolated and its nuclear magnetic resonance spectra was identical to undecaprenol. The membrane fractions from both strains also incorporated glucose from UDP-glucose into glycogen and into a polymer that behaved like Escherichia coli lipopolysaccharide. Conditions were found where the incorporation of glucose could be directed specifically into each compound by adding the appropriate inhibitors.

Second-site mutations in capR (lon) strains of Escherichia coli K-12 that prevent radiation sensitivity and allow bacteriophage lambda to lysogenize

capR (lon) mutants of Escherichia coli K-12 are mucoid and sensitive to ultraviolet (UV) and X-ray radiation as well as to nitrofurantoin. The mutants form filaments after exposure to these agents. capR mutants are also conditionally lethal since they die when plated on complex medium even without UV treatment; this phenomenon is designated "complex medium-induced killing". Furthermore, capR mutants are poorly lysogenized by bacteriophage lambda. Second-site revertants were isolated by plating on media containing nitrofurantoin. All 17 of the independent revertants studied were still mucoid but resistant to UV radiation. Sixteen of the 17 revertants contained a mutation, sulA, that cotransduced with pyrD (21 min). A second locus, sulB, was also found that cotransduced with leu (2 min). Studies with partial diploids (F'pyrD+ sulA+/pyrD36 sulA17 capR9 (lon) demonstrated that sulA+ is dominant to sulA; thus the indicated partial diploid is UV sensitive, whereas the haploid parent is UV resistant. Furthermore, two other phenotypic traits of capR (lon) mutants were reversed by the sul mutation:complex medium-induced killing and the inability of lambda phage to efficiently lysogenize capR strains. On the basis of these and other results, the following model is suggested to explain capR (lon) and sul gene interactions. capR (lon) is a regulator gene for the structural genes sulA+ and sulB+. Depression of both sul operons results in UV sensitivity and decreased ability of lambda to lysogenize, whereas inactivation of either sul+ protein by mutation to sul prevents these phenomena.

Cloning of Escherichia coli DNA that controls cell division and capsular polysaccharide synthesis

A 2 x 10(6) dalton DNA fragment that controls cell division, capsular polysaccharide synthesis, and enzymes of capsular polysaccharide synthesis has been cloned.

Regulation of bacterial cell division: temperature-sensitive mutants of Escherichia coli that are defective in septum formation

Mutations ts2158 and ts1882, which confer temperature sensitivity of septum formation, map near leu in the region of min 2.0 to 2.1 on the Escherichia coli chromosome. These mutants stop division abruptly and grow as filaments at 42 C; when returned to 28 C, division resumes after about 30 min to produce short cells. The product of the gene defined by these mutations probably is required during all stages of septum formation rather than specifically for initiation of septation. Filaments that formed at 42 C contained incomplete constrictiions (septa). When actively dividing filaments (i.e., those incubated at 28 C until division resumed) were shifted to 42 C a second time, division again stopped abruptly and incomplete constrictions persisted during the incubation at 42 C. Filaments that were subjected to 28 C incubation for a brief time (10, 20, or 30 min) before being shifted again to 42 C did not resume division as would be expected of a strain defective in initiating septation. Mutations ts 1882 and ts2158 and recessive to the ts+ allele, which is consistent with the interpretation that these mutations cause the loss of a function. They did not complement each other and presumably represent one cistron. Mutants carrying ts1882 and ts2158 mutations were compared with a mutant defective in the ftA allele, also known to map near leu.

Regulation of galactose operon at the gal operator-promoter region in Escherichia coli K-12

The capR (lon) product controls expression of the gal operon independently of the galR repressor. Previously, mutations of the gal operon have been isolated that are semiconstitutive and alter response to the capR and/or capT product. Such mutants imply the existence of a distinct site in the operon that responds to capR (capT) control. This mutation could be either in a site near the operator-distal end of the galE gene, which signals rho factor termination of transcription in vitro or in a site in the operator-promoter region. Bacteriophage U3 was used to isolate galE mutations in HC2142 (a mutant exhibiting reduced response to capR control). P1 transduction was used to cross these mutants with a set of galE gene deletion. Analysis of the resulting Gal+ recombinants indicates that the regulatory site is in the operator-promoter region. Hence, it is unlikely that capR functions in control as an anti-rho factor at the operator-distal end of the galE gene, but more likely as previously suggested, at a second operator distinct from one responding to galR repressor control. Upon induction with D-fucose, a promoter mutant (UV211) isolated previously expressed 20 to 30% of the galactose enzymes that the wild type exhibited in the presence of the inducer D-fucose. The effects of various mutations in cya, capR, and galR on galactokinase synthesis in this mutant were determined. Galactokinase was derepressed by capR as well as galR, but the presence or absence of the cya gene product was unimportant.

Mapping of sul, the suppressor of lon in Escherichia coli

The suppressor sul, which is allele specific for the ultraviolet sensitivity gene lon, has been mapped by conjugation and transductional crosses in Escherichia coli K-12 and B/r. Previously, sul was reported to lie in the azi region of the Escherichia coli chromosome. Evidence is presented which positions sul close to and clockwise of fabA on the Escherichia coli map. Cotransductional frequencies of 31.3% were obtained between sul and pyrD, and frequencies of 82% were obtained between sul and fabA. Also, the mucoid phenotype of K-12 lon strains grown on minimal glucose agar plates at 37 C was not significantly effected in sul derivatives. No differences between the sul of Escherichia coli B/r and that of K-12 derivatives with regard to map location or effect on mucoid production were observed.

Characterization of mucoid mutants of Escherichia coli K-12 isolated after exposure to ozone

Seventy mucoid mutants retaining the phenotypic properties of the ultraviolet-induced lon strains of Escherichia coli K-12 were isolated after treatment of strain MQ259 (lon+) with ozone. They produce mucoid colonies at 37 C on minimal agar, are abnormally sensitive to radiation, and tend to grow in long aseptate filaments after irradiation with ultraviolet light. Results indicate also that ozone sensitivity, radiosensitivity, and mucoidy are pleiotropic properties of the lon gene.

Multiple regulation of the galactose operon-genetic evidence for a distinct site in the galactose operon that responds to capR gene regulation in Escherichia coli K-12

Previous results demonstrated that the capR (lon) locus, which is not linked to the gal operon, independently controls the synthesis of the gal operon enzymes and gal mRNA, i.e., galO(+)capR9 strains are derepressed 4- to 6-fold as compared to galO(+)capR(+) strains. A mutation has been isolated and localized in the galactose operator region that defines a new and distinct site of control. Mutation in this site, designated galO(capR+), causes a 4-fold increase in the galactose enzymes, galactokinase (EC 2.7.1.6) and UDP-galactose-4-epimerase (EC 5.1.3.2), in a capR(+) background. These mutants exhibit a reduced response to regulation by the unlinked regulator gene capR (lon). However, the galO(capR+) mutants are still subject to control by the galR repressor, since they can be further derepressed by growth in the presence of D-fucose. They also synthesize more galactokinase when grown in glycerol as compared to glucose. Thus there are now at least three, and probably four, sites for control of mRNA synthesis in the operator-promoter regions of the gal operon, making it one of the most complex control systems to date for a single operon in bacteria. The complexity is sufficient to accommodate models for differentiation in higher organisms that require more than one "switch" to control a single group of genes.

The lon Gene and Degradation of β-Galactosidase Nonsense Fragments

N-terminal beta-galactosidase fragments are rapidly degraded in growing cells of Escherichia coli. Mutations in the lon gene are sufficient to enhance the stability of these polypeptides.

Derepression of uridine diphosphate-glucose pyrophosphorylase (galU) in capR(lon), capS, and capT mutants and studies on the galU repressor

Mutation of the capR(lon), capS, or capT genes in Escherichia coli K-12 causes overproduction of capsular polysaccharide leading to a mucoid phenotype. Several of the enzymes involved in capsular polysaccharide synthesis are derepressed in cap mutants. Previously it was shown that uridine diphosphate-glucose (UDPG) pyrophosphorylase, an enzyme involved in the synthesis of three of the nucleotide sugar precursors of the capsule, is derepressed in capR mutants. The control of galU, the gene which codes for UDPG pyrophosphorylase, is described in this study. In addition, it has been found that the enzyme is also derepressed in capS and capT mutants. The effect of galU gene dosage in cap mutants and the wild-type strain (all lysogenic for phi80) was studied by infecting them with the purified transducing phage phi80dgalU. The level of UDPG pyrophosphorylase increased in proportion to the number of galU copies added. The rate of enzyme synthesis in the mutants was about sixfold higher than in the wild type per galU gene added for multiplicities of infection from one to twenty. Thus, all the galU copies added to the wild-type lysogen were repressed. We obtain greater than 20 galU copies per cell by infecting the nonlysogenic strain which allows multiplication of phi80dgalU. With some number of galU copies greater than 20, the rate of UDPG pyrophosphorylase synthesis in the wild type approaches the mutant rate of synthesis. The results suggest that there may indeed be a galU repressor pool in the cell which can be completely titrated. This pool must be composed of more than 20 galU repressor molecules. Since the capR, capS, and capT gene products or combinations thereof are known to control other widely separated operons of the cell besides the galU gene, it is postulated that the galU repressor may be capable of binding other operators. This would account for the relatively large pool of galU repressors per cell.

Tyrosine and phenylalanine biosynthesis in Escherichia coli K-12: complementation between different tyrR alleles

Dominance tests in diploids have confirmed that the product of the tyrR gene is involved in a negative control system affecting the synthesis of both 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and DAHP synthetase (phe). Some tyrR mutants are derepressed for the synthesis of both DAHP synthetase (tyr) and (phe), whereas others are derepressed for the synthesis of DAHP synthetase (tyr) but overrepressed for the synthesis of DAHP synthetase (phe). Complementation tests between these alleles confirm that they are in the same cistron. The allele causing overrepression of enzyme synthesis is dominant over both the wild type and the derepressing allele in diploids.

In vitro repression of the transcription of gas operon by purified gal repressor

We have studied the in vitro repression of gal mRNA synthesis by the gal repressor from Escherichia coli. By use of a four-step purification procedure involving chromatography on phosphocellulose, DEAE-cellulose, and an affinity resin, the gal repressor has been purified about 1600-fold from a crude cell extract. The purification was aided by use of a cell extract made after prophage induction of cells lysogenic for bacteriophage lambda that carries the gal repressor gene (galR). The highly purified gal repressor is an effective and specific repressor of in vitro synthesis of gal mRNA with lambda gal DNA as template. Both D-fucose and D-galactose overcome the action of gal repressor; the half-maximal concentrations of D-fucose and D-galactose for overcoming the action of repressor are 1 mM and 0.5 mM, respectively. The repressor fails to repress gal-specific transcription when the gal DNA contains a cis-dominant operator constitutive (O(c)) mutation. We conclude that the gal repressor recognizes the gal operator site and acts by preventing gal transcription.

New amino acid regulatory locus having unusual properties in heterozygous merodiploids

Spontaneous mutants of Escherichia coli B/r resistant to 5',5',5',-trifluoro-dl-leucine contain defects in a gene which maps to the left of the threonine region. Low-level constitutive expression of the isoleucine-valine and leucine operons is caused by this mutation in haploid strains. This is in contrast to extremely high levels of gene expression in the heterozygous merodiploids (F' wild type/mutant allele). The properties of these mutants define a new locus and suggest that it encodes a subunit protein which is involved in the repression of the structural genes for the branched-chain amino acid pathways.

Multiple regulator gene control of the galactose operon in Escherichia coli K-12

Previous studies showed that nonsense mutations in either of two genes (capR or capS) or an undefined mutation in a third gene (capT) led to pleiotropic effects: (i) increased capsular polysaccharide synthesis (mucoid phenotype); (ii) increased synthesis of enzymes specified by at least four spatially separated operons involved in synthesis of capsular polysaccharide including the product of the galE gene, UDP-galactose-4-epimerase (EC 5.1.3.2) in capR mutants. The present study demonstrated that the entire galactose (gal) operon (galE, galT, and galK) is derepressed by mutations in either the capR or the capT genes, but not by mutation in capS. Double mutants (capR9 capT) were no more derepressed than the capR9 mutant, indicating that capR9 and capT regulate the gal operon via a common pathway. Isogenic double mutants containing either galR(+), galR(-), galR(s), or galO(c) in combination with either capR(+) or capR9 were prepared and analyzed for enzymes of the gal operon. The results demonstrated that capR9 caused derepression as compared to capR(+) in all of the combinations. Strains with a galR(s) mutation are not induced, for the gal operon, by any galactose compound including d-fucose, and this was confirmed in the present study using d-fucose. Nevertheless, the derepression of galR(s) capR9 compared to galR(s) capR(+) was four- to sixfold. The same derepression was observed when galR(+)capR9 was compared to galR(+)capR(+). The data eliminate the explanation that internal induction of the gal operon by a galactose derivative was causing increased gal operon enzyme synthesis in capR or capT mutants. Furthermore, the same data suggest that the galR and capR genes are acting independently to derepress the gal operon. A modified model for the structure of the gal operon is proposed to explain these results. The new feature of the model is that two operator sites are suggested, one to combine with the galR repressor and one to combine with the capR repressor.

Differential depression of staphylococcal plasmid and chromosomal penicillinase genes by a class of unlinked chromosomal mutations (R2-)

We described previously a class of mutations (phenotypic designation R2(-)) in Staphylococcus aureus that were unlinked to penicillinase genes but nevertheless imposed constitutive synthesis of this enzyme upon wild-type plasmids. The plasmids affected by these mutations have been found to possess the same maintenance-compatibility type (I) and to form penicillinase of serotype A. Three plasmids that had a different maintenance-compatibility type (II) and formed penicillinase of serotype C were only slightly derepressed in R2(-) mutants. Three chromosomal penicillinase genes were variably derepressed, the range extending from negligible to nearly complete derepression. The differences in degree of derepression among the three types of penicillinase linkage groups were tentatively ascribed to position effects.

Genetics of a chain-forming mutant of Escherichia coli. Transduction and dominance of the envA gene mediating increased penetration to some antibacterial agents

We have recently described a chain-forming mutant ofEscherichia coliwhich showed a decreased resistance to ampicillin and several other antibiotics (Normark, Boman & Mattson, 1969). The gene mediating drug sensitivity was denotedenvAand by conjugation mapped at 2–4 min. Transduction experiments have now shown thatenvAis located betweenleuandaziat 1·5 min. The mapping was facilitated by the finding thatenvAmediated sensitivity to actinomycin D, rifampicin and gentian violet. TheenvAlocus could be genetically differentiated from thepealocus mediating resistance to phenethyl alcohol (Yura & Wada, 1968). Studies using partial diploids revealed thatenvAwas recessive to its wild-type allele both when located on an episome and on the chromosome.

Assuming that revertants fromenvAto the wild-type allele could be selected as ampicillin-resistant derivatives, such mutants were isolated and their phenotype characterized. Reversion to ampicillin resistance was accompanied by reversion to insensitivity to actinomycin D. However, not all revertants exhibited wild-type tolerance to rifampicin. Three different ampicillin-resistant revertants were studied genetically. The results indicate that these strains contain suppressor mutations in theenvAregion of the chromosome. It is suggested that theenvAgene, directly or indirectly, affects the EDTA sensitive ‘permeability barrier’ of the surface layer ofEscherichia coli.

Control of colanic acid synthesis

The nucleotide pools of certain mucoid, colanic acid-synthesizing strains of Escherichia coli, Salmonella typhimurium, and Aerobacter cloacae were examined, and in all cases the nucleotide sugars uridine-5'-diphosphate glucose (UDPG), uridine-5'-diphosphate galactose (UDPGal), guanosine-5'-diphosphate fucose (GDPF), and uridine-5'-diphosphate glucuronic acid (UDPGA) were detected. It is postulated that these nucleotide sugars are precursors in the synthesis of colanic acid. The levels of these nucleotide sugars and of the enzymes involved in their synthesis were examined in a number of mucoid strains and compared with the levels found in certain strains which were repressed in the synthesis of colanic acid, only becoming mucoid when grown in the presence of p-fluorophenylalanine (PFA). The levels of UDPG and UDPGal and the enzymes involved in their synthesis were substantially the same in both mucoid and repressed types, but the levels of UDPGA and GDPF and of some of the enzymes involved in their synthesis were much higher in mucoid strains. When repressed strains were grown in the presence of PFA, the levels of UDPGA and GDPF approached those found in mucoid strains. The existence of an operon, containing genes coding for certain key enzymes involved in colanic acid synthesis has been suggested.

Depression of guanosine diphosphate-mannose pyrophosphorylase by mutations in two different regulator genes involved in capsular polysaccharide synthesis in Escherichia coli K-12

Mutations in a regulator gene (capR) that causes increased synthesis of capsular polysaccharide and derepressed synthesis of several enzymes involved in polysaccharide synthesis also derepress synthesis of guanosine diphosphate (GDP)-mannose pyrophosphorylase. In addition, a second mucoid mutation (capS, which maps separately from capR) also results in the derepression of GDP-mannose pyrophosphorylase. New conditions for assaying GDP-mannose hydrolyase and GDP-l-fucose synthetase permitted us to show that these enzymes are also derepressed in the capS mucoid strain. Although phosphomannose isomerase and uridine diphosphate-galactose-4-epimerase are derepressed in capR mucoid strains, they are not derepressed in capS mucoid strains. A nonmucoid mutant of a strain containing the capR9 (mucoid) allele was deficient in GDP-mannose pyrophosphorylase.

Resistance of Escherichia coli to penicillins. 8. Physiology of a class II ampicillin-resistant mutant

Class II ampicillin-resistant mutants of Escherichia coli are defined as having a twofold increase in penicillinase-mediated ampicillin resistance when determined by colony formation tests on plates. In this paper, one class II mutant has been compared to its parent strain. In liquid medium, the mutant was less resistant than the parent strain both in the absence and in the presence of R1 and R-factor mediating penicillinase activity. The penicillinase activity was found to be almost completely bound to the cells in the parent strain, whereas it was excreted to a great extent in the class II mutant strain. In liquid medium, resistance was well correlated to the cell-bound penicillinase activity, whereas the excreted penicillinases were also of great importance for survival on ampicillin plates. The mutant also had a changed resistance to a great number of other antibacterial drugs. The mutant was found to be more sensitive than the parent strain to osmotic shock, especially when treated with ethylenediaminetetraacetic acid or washed with sodium ions. However, the osmotic stability was restored by the presence of 1 mm Mg(2+) ions. The class II mutant was more sensitive than the parent strain to sodium cholate, and it adsorbed the phages T4 and T3-1 at a slower rate than did the parent strain. The two strains adsorbed T6 at the same rate. The class II phenotype could be gradually reversed by increasing concentrations of divalent cations. The pleiotropic changes in the phenotype are apparently unrelated to the specific targets for the antibacterial agents tested. They are secondary consequences of a cell envelope mutation. The findings indicate that the class II mutation mediates a structural change in the lipopolysaccharide of the cell envelope.

Control of uridine diphosphate-glucose dehydrogenase synthesis and uridine diphosphate-glucuronic acid accumulation by a regulator gene mutation in Escherichia coli K-12

Uridine diphosphate (UDP)-glucose dehydrogenase, the enzyme that converts UDP-glucose to UDP-glucuronic acid, was derepressed in a mucoid (capR9) strain of Escherichia coli K-12 and repressed in a nonmucoid (capR(+)) strain. A nonmucoid mutant (strain MC 152; capR9 non-2) derived from the mucoid strain accumulated large quantities of nucleotides. Among these nucleotides, UDP-glucuronic acid was identified as well as guanosine triphosphate and an adenosine diphosphate-sugar. UDP-glucose dehydrogenase was still derepressed in strain MC 152. When the nonmucoid mutant was transduced to the wild-type state for this regulator gene (capR(+)), the transductant was found to accumulate less total nucleotides, and the accumulation of UDP-glucuronic acid was abolished. UDP-glucose dehydrogenase was repressed in the capR(+)non-2 strain but not to the same extent that it was in the capR(+) strain.

Derepression of GDP-alpha-mannose and UDP-glucose pyrophosphorylases by a regulator gene mutation; episomal dominance in partial diploids

Mutants of Escherichia coli K12 at the capR locus are overproduce capsular polysaccharide, and are derepressed for synthesis of several enzymes involved in capsular polysaccharide synthesis(1-3) including GDP-mannose pyrophosphorylase.(8) UDP-glucose pyrophosphorylase is also derepressed in a haploid capR9 mucoid mutant. Heterozygous mucoid partial diploids with the capR9 allele on the episome and the wild-type (capR(+)) allele on the chromosome (F'capR9/capR(+)) are derepressed for UDP-glucose pyrophosphorylase and GDP-mannose pyrophosphorylase, while the reciprocal nonmucoid heterozygotes (F'capR(+)/capR9) are repressed for these enzymes. These results provide evidence that the episomal capR allele is dominant with respect to synthesis of these two enzymes.

Structural studies on colanic acid, the common exopolysaccharide found in the enterobacteriaceae, by partial acid hydrolysis. Oligosaccharides from colanic acid

The exopolysaccharide slime colanic acid has been isolated from representative strains of Escherichia coli, Salmonella typhimurium and Aerobacter cloacae. Analysis showed that each polymer contained glucose, galactose, fucose and glucuronic acid, together with acetate and pyruvate. The molar proportions of these components were 1:1.8:1.9:1:1:1 approximately. On the basis of periodate oxidation of the natural and deacetylated polysaccharide, glucose is proposed as the site of the acetyl groups. The pyruvate is attached to galactose. Three neutral oligosaccharides and ten electrophoretically mobile oligosaccharides were isolated and partially characterized. Four of the fragments were esters of pyruvic acid. Most oligosaccharides were isolated from all three polysaccharide preparations. Three further oligosaccharides were isolated from carboxyl-reduced colanic acid and sodium borotritide was used to label the glucose derived from glucuronic acid in these fragments. One trisaccharide was obtained from periodate-oxidized polysaccharide. On the basis of these oligosaccharides a repeating hexasaccharide unit of the following structure is proposed: [Formula: see text] The significance of this structure in colanic acid biosynthesis is discussed.

Exopolysaccharide colanic acid and its occurrence in the Enterobacteriaceae

A study of strains from the genera Salmonella, Escherichia, and Aerobacter has shown that under appropriate conditions many strains produce an exopolysaccharide slime of identical composition, which has been identified as colanic acid on the basis of its chemical composition and its sensitivity to certain bacteriophage-induced depolymerase enzymes. Chemical analysis shows that the polysaccharide contains O-acetyl groups in addition to the sugars glucose, galactose, fucose, and glucuronic acid. Mild acid hydrolysis has led to the isolation of a beta-glucosylfucose in addition to glucuronic acid containing oligosaccharides. Many strains were found to synthesize colanic acid under normal conditions of growth or under conditions favoring polysaccharide synthesis, whereas others only synthesized colanic acid when the control mechanism was derepressed by p-fluorophenylalanine.

Dominance of ultraviolet radiation resistance in partial diploids of Escherichia coli K-12

Although an F'13 capR(+)/capR9 strain is nonmucoid and an F'13 capR9/capR(+) strain is mucoid, both strains are ultraviolet (UV)-resistant. In contrast, haploid capR9 strains are UV-sensitive. Therefore, UV resistance is dominant to UV sensitivity, regardless of whether the capR(+) allele is on the chromosome or on the F'13 episome.

Positive control of sulphate reduction in Escherichia coli. The nature of the pleiotropic cysteineless mutants of E. coli K12

1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB(+) is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE(+) is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0.2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.

Derepression of beta-galactosidase synthesis in Escherichia coli K-12 by p-fluorophenylalanine

p-Fluorophenylalanine (FPA) derepresses beta-galactosidase synthesis at 35 C but not at 25 C in Escherichia coli K-12, strain MC132 (lac I1,2), a strain with a temperature-sensitive lac repressor. In contrast, strain MC130 (lac I(+)) is not derepressed by FPA at 35 C. Temperature-shift experiments with strain MC132 in the presence of FPA and other reagents (isopropyl-1-thio-beta-d-galactoside or chloramphenicol) are consistent with the following mechanism. FPA is incorporated into the genetically altered lac repressor at all temperatures. This further alteration due to incorporation of analogue makes the lac repressor protein inactive at 35 C but active at 25 C. Once an active tertiary structure is formed at 25 C, it is stable at 35 C. However, the inactive tertiary structure of the FPA-containing repressor can assume an active tertiary structure when the temperature is shifted from 35 to 25 C. In the discussion of the results, "inactive tertiary structure" is equated with "monomers" and "active tertiary structure" with oligomers.

P1-mediated transduction of a gene that controls radiation sensitivity and capsular polysaccharide synthesis from Shigella dysenteriae to Escherichia coli

When Shigella dysenteriae strain 60 is used as a donor and Escherichia coli K-12 strains that are ultraviolet (UV)-sensitive, mucoid, and proline-requiring (Pro(-)) are employed as recipients, selection for Pro(+) yields 2 to 6% nonmucoid clones. All of the nonmucoid clones examined are UV-resistant. Most of the nonmucoid UV-resistant transductants are partial diploids for the genes being studied. When these Shigella-Escherichia hybrids are used as donors with the same E. coli recipients, the cotransduction of Pro(+) and nonmucoidness is greatly increased (59 to 94% cotransduction). All of these nonmucoid transductants examined were also UV-resistant. The results indicate that Shigella contains an allele (designated ShproC(+)) homologous to proC of E. coli and a second linked allele (designated ShcapR(+)) homologous to the capR allele of E. coli. The ShcapR(+) allele changes the phenotype of certain E. coli strains from mucoid UV-sensitive (capR6) or very sensitive (capR9) to nonmucoid and UV-resistant. Unanticipated capR allele interactions in the partial diploid hybrids are described.

Ultraviolet sensitivity gene of Escherichia coli B

The ultraviolet sensitivity gene of Escherichia coli B was introduced into a K-12 recipient by transduction with phage P1. The uvs gene of E. coli B is cotransducible with the proC locus of K-12, is closely linked to tsx, is not linked to lacZ, and only rarely to purE. The transductants are mucoid, filamentous on irradiation, and show plating-medium response. The order of markers is lacZ proC tsx uvs purE.