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Biomedical subjects

C Blanco

Publications and source records attributed to C Blanco.

At least 145 records · Page 8Linked to original sources
PubMed1988

Isolation and preliminary characterization of twenty bacteriophages infecting either brevibacterium or arthrobacter strains.

Thirty-seven bacteriophages plaquing on Corynebacterium, Brevibacterium, or Arthrobacter strains were isolated from soil or vegetation samples. Restriction analysis of phage DNA indicated that 20 phages were unique; one of them produced entirely turbid plaques on Brevibacterium ketoglutamicum and was characterized as temperate. All these phages were assigned to group B of the classification of Bradley (Bacteriol. Rev. 31:230-314, 1967) and had relatively narrow host ranges.

Journal Article↗
PubMed1987

Transcriptional and translational signals of the uidA gene in Escherichia coli K12.

The expression of uidA is negatively controlled by the products of the uidR and uxuR genes and is sensitive to catabolite repression. The locations of the transcriptional and translational signals of uidA were determined using lac gene fusions and S1 mapping experiments. The promoter structure of uidA resembles that of a promoter activated by cAMP receptor protein (CRP); putative control regions are located at positions -10 and -35 (relative to the transcription start site), are separated by more than 17 bp and exhibit poor homology with the normally recognized consensus sequences. Moreover, 80 bp separate the promoter from the translational signals. No CRP binding site was detected in the promoter region of uidA. Two operator sites, 01 and 02, were identified: 01 has a greater affinity for the UidR repressor, whereas 02 has a greater affinity for the UxuR repressor, but the two repressor molecules are able to bind at both the 01 and 02 sites. Analysis of two operator constitutive mutations allowed the location of one of the two UidR repressor binding sites; it contains palindromic units spanning the TaqI site of the uidA control region.

Base Sequence↗
PubMed1987

One step purification of Escherichia coli beta-glucuronidase.

beta-glucuronidase was purified by affinity chromatography on thiophenyl-glucuronide coupled to Sepharose. The enzyme was more than 95% pure. This enzyme is a tetramer composed of identical 74 kDa monomers. The amino-terminal sequence determined was: NH2-Met-Leu-Arg-Pro-Val.

Amino Acid Sequence↗
PubMed1987

Characterization of the corynebacteriophage CG33.

Bacteriophage CG33 was isolated from a strain of Corynebacterium glutamicum that had become contaminated during an industrial fermentation. CG33 was assigned to Bradley's group B since it had a polyhedral head 40 nm wide and a short non-contractile and striated tail 78 nm long. Adsorption to its host, C. glutamicum ATCC 13287, was enhanced in the presence of Ca2+. The latent period was 18 min at 34 degrees C; the burst size was 16 p.f.u. ml-1. CG33 also formed plaques on C. lilium ATCC 15990 but at a low frequency. Its genome consisted of a linear double stranded DNA molecule of 13.4 kb with cohesive ends. A restriction map of the genome was obtained by using various endonucleases.

Bacteriophages↗
PubMed1987

Structural characteristics of the Corynebacterium lilium bacteriophage CL31.

Bacteriophage CL31 was isolated on a Corynebacterium lilium strain. Out of 30 strains tested, only CL31 was able to form plaques on Corynebacterium glutamicum ATCC 13287, Brevibacterium lactofermentum ATCC 21086, and Arthrobacter sp. strain SI55, but at a very low frequency. This phage belongs to group B of Bradley's classification (D. E. Bradley, Bacteriol. Rev. 31:230-314; 1967). Its head is 53 nm in diameter, and its tail is 396 nm in length. The phage capsid contains three major proteins, of 12.5, 29.0, and 37.0 kilodaltons, and five minor ones (23.9, 26.0, 27.0, 40.0, and 55.4 kilodaltons). CL31 DNA is a linear molecule of 48 kilobases with cohesive ends. Restriction mapping was performed for endonucleases BglII, EcoRI, SalI, and KpnI. The expression of CL31 genes in Escherichia coli was studied by the maxicell technique; 12 different proteins were detected.

Bacteriophages↗
PubMed1986

The regulatory region of the uxuAB operon in Escherichia coli K12.

The uxuAB operon is composed of two genes coding for enzymes involved in hexuronate degradation. This operon is negatively controlled by the uxuR and exuR regulatory gene products. Starting from uxu hybrid plasmids, a 300 bp Sau3A restriction fragment was isolated and shown to contain the entire uxu regulatory region using in vitro gene fusions that brought lac gene expression under the control of the transcriptional and translational signals of the uxuA gene. The nucleotide sequence of this fragment was established. The start of the uxu mRNA was localized by S1 mapping experiments (the presence of a CAP binding site upstream of the promoter was shown by DNAse I footprinting and in vitro titration). The N-terminal amino acid sequence of the purified uxuA-lacZ gene product allowed the mapping of the uxuA initiation codon at 115 bp from the start of transcription.

Base Sequence↗
PubMed1986

Negative dominant mutations of the uidR gene in Escherichia coli: genetic proof for a cooperative regulation of uidA expression.

The uidA gene is the first gene involved in the hexuronide-hexuronate pathway in Escherichia coli K-12 and is under the dual control of the uidR and uxuR encoded repressors. Point mutations affecting the uidR regulatory gene were sought to investigate the regulation of uidA. When the uidR mutant allele was on a multicopy plasmid and the wild-type allele was on the chromosome, some of the mutant phenotypes were dominant to the wild-type phenotype, indicating that the active form of the UidR repressor is multimeric. We have demonstrated that expression of the mutant phenotype is dependent on gene dosage. The dominance of the uidR allele was also sensitive to the presence of the wild-type uxuR allele in the cell. This behavior probably results from UidR-UxuR repressor interactions. A mechanism is proposed: we suggest that the UidR and UxuR repressors interact after their binding to the operator site of uidA; the binding of one regulatory molecule may facilitate the binding of the other one in a cooperative process.

Enzyme Induction↗
PubMed1986

A DNA sequence containing the control sites for the uxaB gene of Escherichia coli.

The nucleotide sequence of a 286 bp fragment containing the uxaB control region of Escherichia coli has been determined. The transcriptional start of the uxaB gene has been located and the promoter signals identified. Various fragments of the uxaB promoter-proximal region were fused in vitro with the lacZ gene. Results obtained with these fusions indicate that the operator-promoter sites are located on a 110 bp restriction fragment. The determination of the amino acid sequence of the NH2-terminus of the uxaB gene product revealed that the uxaB gene is not initiated with the AUG codon but with the unusual GTG codon. CRP, the cyclic AMP receptor protein, does not bind to the uxaB control region DNA even though expression of the uxaB gene is sensitive to catabolite repression.

Amino Acid Sequence↗
PubMed1985

Nucleotide sequence of a regulatory region of the uidA gene in Escherichia coli K12.

Multiple regulatory events are involved in the expression of the uidA gene. A regulatory region of this gene has been located on a 460 base pair Sau3A-EcoRI fragment and its nucleotide sequence was determined by the dideoxy method using pEMBL plasmids. A preliminary analysis of this sequence revealed the presence of numerous palindromic structures with some overlaps.

Base Sequence↗
PubMed1985

Genetic analysis of uxuR and exuR genes: evidence for ExuR and UxuR monomer repressors interactions.

The uxuAB operon is under the dual control of uxuR- and exuR-encoded repressors whereas the exu regulon genes are regulated by the sole ExuR repressor. Mutations affecting the two exuR and uxuR regulatory genes were selected to investigate the relationship between the two repressors. The isolation of exuR and uxuR negative dominant mutations on a multicopy plasmid indicated that the active form of the two repressors was multimeric. The introduction of a uxuR negative dominant allele into a wild-type strain resulted in a significant increase in exu gene expression. This unexpected effect may have been the consequence of the formation of hybrid repressor molecules. This protein must be composed of native ExuR+ subunits aggregated with altered UxuR subunits. The same interference was observed for the exuR negative dominant allele on uxu gene derepression. The hypothesis given here implies that the two regions of the ExuR and UxuR repressors involved in the subunit aggregation present enough homologies to allow the formation of hybrid repressor molecules.

Carbohydrate Dehydrogenases↗
PubMed1985

The use of gene fusions to study the expression of uidR, a negative regulatory gene of Escherichia coli K-12.

The uidR regulatory gene of Escherichia coli codes for a repressor molecule that negatively controls the expression of the uidA gene. The uidR gene was fused in front of the lacZ gene in vitro on plasmid cloning vectors developed by Casadaban et al. [J. Bacteriol. 143 (1980) 971-980. The transcriptional direction of uidR was deduced from the restriction pattern and the phenotypic properties of the uidR-lacZ fusion plasmids. The gene is transcribed counterclockwise on the standard E. coli map, as is the uidA gene. The uidR-lacZ fusions were also used to examine the regulation of expression from the uidR promoter. It was observed that the uidR gene expression is repressed by its own product and is sensitive to catabolite control. The uidR-lacZ-encoded proteins of various sizes were isolated but attempts to obtain hybrid molecules possessing, in a single polypeptide, both the beta-galactosidase and UidR repressor activities were unsuccessful.

Chimera↗
PubMed1984

Relative independence of metabolic enzymes and neuromuscular activity.

Effects of spinal cord transection in 2-wk-old cats on the metabolic, histochemical, and fatigue properties of a fast- and a slow-twitch muscle were determined. Chronic (6-12 mo) spinalization (Sp) resulted in an increased ratio of fast-twitch, oxidative-glycolytic (FOG) to slow-twitch, oxidative (SO) fibers in soleus (SOL). In medial gastrocnemius (MG), Sp produced a histochemical profile suggesting that fast fibers were increased at the expense of slow fibers. Changes in biochemical markers for oxidative (citrate synthase) and glycolytic (GPD) potential were consistent with the histochemical findings. The fatigue index of Sp MG and SOL remained normal and was consistent with the type and degree of fiber type change. Daily treadmill exercise did not markedly alter any of the adaptations. The metabolic and fatigue properties of skeletal muscle of Sp cats are consistent with the view that as some fibers develop "faster-like" characteristics, the oxidative and the glycolytic potential is also enhanced. As was true of the contractile properties and related biochemical data, the changes observed suggest that significant changes occurred within as well as across fiber types. These data, in conjunction with that of chronic EMG recordings, provide evidence that there is a relative independence of both the oxidative potential and the fatigability of a muscle relative to its quantity of activation.

Animals↗
PubMed1983

Interchangeability of repressors for the control of the uxu and uid operons in E. coli K12.

The uidA and uxuAB operons are each under the dual control of two repressor molecules: the uidR and uxuR encoded repressors negatively control the uidA operon whereas the uxuAB operon is regulated by the uxuR and exuR gene products. Plasmids overproducing the regulatory molecules encoded by exuR, uxuR, or uidR were used to investigate the regulation of these two operons. Large amounts of either exuR or uxuR repressor caused a complete repression of the uxuAB operon in exuR and uxuR double-deleted mutants, suggesting that the two repressors, when they are overproduced, are totally interchangeable for the control of the uxuAB operon. In contrast, the UxuR molecule has no effect on the other exu regulon operons controlled by the exuR gene product. The uidR and uxuR gene products appear to be partially interchangeable for the regulation of the uidA gene since addition of multicopy plasmids bearing uidR+, in uxuR deleted mutant strains, only partially suppresses the derepression of the uidA gene. Inversely, multicopies of uidR weakly reduced the synthesis of the uxuB gene product in uxuR derepressed mutants. The restrictions placed by these phenomena on the formulation of the mechanism of cooperation between the two repressor molecules for repressing the uxuAB and uidA operons are discussed.

Escherichia coli↗
PubMed1983

Characterization of the operator sites of the exu regulon in Escherichia coli K-12 by operator-constitutive mutations and repressor titration.

In Escherichia coli, the exu regulon of the hexuronate system involves the three exuT, uxaCA and uxaB operons and is under the negative control of the exuR regulatory gene product. The technique developed by Casadaban, Chou and Cohen was employed to construct two plasmids containing operon fusions in which the lactose genes were fused to the uxaCA and exuT operons. These fusions were transferred into the chromosome by a reciprocal recombination event, and the resulting strains were used for isolation of mutants defective in repression. Two types of operator-constitutive mutants were obtained: one specific for the uxaCA operon expression and the other affecting the exuT gene expression. This genetic evidence confirms that these two operons which are divergently transcribed each possess their own operator site.--The derepressed expression of the two exuT-lac and uxaCA-lac operons and the uxaB gene was also examined upon introduction of plasmids bearing various operators of the exu regulon. The results of testing exuR repressor titration by multiple copies of the exu operators allowed us to show a gradation in the affinity degrees for the three exu operators: uxaBo has the strongest affinity for the exuR repressor and uxaCo the weakest, although that of exuTo seems to be just slightly greater. This gradation may play a role in the control of the exu regulon expression.

Chromosomes, Bacterial↗
PubMed1983

Construction of hybrid plasmids containing the Escherichia coli uxaB gene: analysis of its regulation and direction of transcription.

The uxaB gene of Escherichia coli, encoding for altronate oxidoreductase involved in the hexuronate degradative pathway, was isolated on a ColE1-uxaB hybrid plasmid from the Clarke and Carbon bank. The restriction map of this plasmid was established. The uxaB gene was mapped on a 1.5-megadalton HindIII-KpnI DNA fragment. Use of an in vitro gene fusion between uxaB and lacZ genes led to the determination that uxaB is transcribed from the KpnI towards the HindIII restriction sites. Gene amplification in cells containing various uxaB hybrid plasmids allowed us to show a gradation in the level of repression of exu operator sites by the exuR regulatory gene product.

Carbohydrate Dehydrogenases↗
PubMed1983

Muscle fiber type distribution and architecture of the cat diaphragm.

Three types of diaphragmatic muscle fibers were identified histochemically in the sternal, costal, and crural regions of the cat diaphragm. Differences in the proportion of each muscle fiber type were observed between the abdominal and thoracic surfaces of the diaphragm but not among the different regions. A higher percentage of slow-twitch oxidative fibers was noted on the abdominal surface, whereas more fast-twitch fibers (fast-twitch oxidative-glycolytic and fast-twitch glycolytic) were found on the thoracic surface. Differences in muscle architecture were observed between diaphragmatic regions, but not between abdominal and thoracic sides. Overall, muscle fibers were longer in the crural regions, with the longest fibers being found in the crossing-band area of the crura. In the costal regions, fibers were longest in the center and became shorter toward the ventral and dorsal extent of these regions. Fiber lengths were similar throughout the sternal region. In each diaphragmatic region, the length of fibers extended from the origin of the muscle to its insertion. We conclude that functional differences between diaphragmatic regions could be attributed to fiber length and/or orientation, but not to differences in fiber-type composition.

Animals↗