Biomedical subjects

C Debouck

Publications and source records attributed to C Debouck.

78 records · Page 5Linked to original sources

PubMed1986

Functional domains of the yeast regulatory protein GAL4.

In the yeast Saccharomyces cerevisiae regulation of the galactose/melibiose regulon rests on a dosage-dependent functional interplay between the positive regulator of transcription, the GAL4 protein, and the negative regulator, GAL80 protein. We have used this interplay to select in vitro generated fusions between the yeast ADH1 promoter and GAL4 coding sequence that overproduce GAL4 protein, allowing the identification of GAL4 protein in crude extracts from yeast. One type of these constructions produces a GAL4 protein that lacks its normal NH2 terminus. This protein is unable to complement a gal4 lesion but still retains a domain that functionally antagonizes the negative regulatory protein. One defect in this truncated protein is its inability to be concentrated in the nucleus. However, the nuclear localization defect is complemented by full-length GAL4 protein. The truncated protein also appears to effect changes in the relative transcriptional levels of the structural genes. These observations imply that GAL4 protein consists of several domains, including ones for nuclear localization, interaction with the negative regulatory protein, and, possibly, separable transcriptional activation domains for the structural genes.

Alcohol Dehydrogenase↗

PubMed1986

Synthesis of the complete trans-activation gene product of human T-lymphotropic virus type III in Escherichia coli: demonstration of immunogenicity in vivo and expression in vitro.

Human T-lymphotropic virus type III (HTLV-III) contains a gene (tat-III) the product of which activates the expression of viral genes in trans. We have expressed in Escherichia coli the complete tat-III-encoded protein as well as a truncated form that lacks three amino acids from the amino terminus. These proteins are recognized by sera of many, but not all, infected individuals including patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex, as well as asymptomatic seropositive persons. Seropositivity for the tat-III protein does not appear to correlate with the clinical stage of HTLV-III-related disease. Antibodies raised in rabbits against the E. coli-produced protein detect the native protein (apparent molecular mass, 14.5 kDa) in a virus-producing cell line. A second protein (26 kDa), of unknown origin but viral related, is also specifically recognized by the immune serum.

Base Sequence↗

PubMed1986

[Early exercise test after revascularization and rehabilitation].

Ergospirometry was performed on 51 patients before their discharge from hospital, that is between the seventh and tenth days after myocardial revascularization by cardiac bypass surgery. The aim of our study is to show that this type of measurement can be performed with reasonable safety and that it gives an accurate assessment of the patient's ability to withstand exercise. It employs a metabolic approach: study of oxygen consumption (V'O2), carbon dioxide release (V'CO2), the respiratory quotient (RQ), the minute ventilation (V'E) and the respiratory equivalent for oxygen (REO2). The patients withstood a mean load of 82 +/- 17.7 watts for a mean V'O2 of 1.186 +/- 0.258 l/min STPD and a mean V'E of 46.5 +/- 10 l/min BTPS. Changes in respiratory and metabolic parameters as a function of load are discussed, as is the advice that can be given to the patient regarding physical rehabilitation.

Adult↗

PubMed1985

Structure of the galactokinase gene of Escherichia coli, the last (?) gene of the gal operon.

We present the nucleotide sequence of the galactokinase gene (galK) of Escherichia coli including its 5' and 3' flanking regions. This DNA sequence derives from the lambda gal8 transducing phage and is identical to the sequence present in the galK gene fusion vectors, pKO and pKG, commonly used to study transcriptional regulatory elements. We define the precise 3' junction between the bacterial and phage sequences in lambda gal8 and demonstrate that this junction probably results from a homologous recombination event between identical 9 bp sequences common to the gal operon and phage lambda. Moreover, we examine the 300 bp region located immediately beyond galK for transcription termination function and find no gal operon terminator. Lastly, we compare the galK genes of E. coli and the yeast S. cerevisiae and find several regions of strong homology among which is a potential ATP-binding site homology shared by a variety of ATP-binding proteins including protein kinases encoded by mammalian oncogenes.

Adenosine Triphosphate↗

PubMed1984

Mutations that alter the DNA binding site for the bacteriophage lambda cII protein and affect the translation efficiency of the cII gene.

The efficiency of translation of the cII gene of bacteriophage lambda is greatly reduced by the cII3059 mutation, a GUU----GAU (Val----Asp) change in the second cII codon. Mutations in the third and fourth codons of the cII gene, called ctr mutations, reverse this translation deficiency. Lambda cII3059 ctr-1, which has a GCA----ACA (Ala----Thr) change in the fourth cII codon, produces about half the normal level of cII activity in liquid cultures, and lambda cII3059 ctr-2 and lambda cII3059 ctr-3, which have identical CGT----CGC changes in the third codon, produce normal levels of cII activity in liquid culture. Since the cII protein of ctr-3 has the same primary sequence as that of lambda cII3059, the cII- phenotype of lambda cII3059 can be explained entirely by the deficiency of translating cII mRNA. We propose that ctr mutations increase translation efficiency by destabilizing a stable stem structure which can be formed by cII mRNA. The ctr mutations lie in an overlapping regulatory region which contains, in addition to sequence elements that influence the rate of cII translation, a region to which cII protein binds to activate transcription from the PRE promoter. The ctr-1 mutation alters the cII recognition sequence from 5'-T-T-G-C-N6T-T-G-C-3' to 5'-T-T-G-C-N6T-T-G-T-3', but has no effect on PRE activity. Since a C----T change in the first (5'-proximal) T-T-G-C sequence (to yield 5'-T-T-G-T-N6T-T-G-C) greatly lowers cII binding affinity, cII protein must not recognize the two T-T-G-C sequences in an identical manner.

Bacteriophage lambda↗

PubMed1983

Regulation of the pR operon of bacteriophage lambda.

The E. coli lambda lysogen, OR1263, carries the fusion pR-cro-tR1-IS2-gal. The gal promoter is deleted and gal expression from pR, in the absence of the lambda antitermination factor N, is blocked by the efficient transcription terminator in IS2. Selection for Gal+ yields strains deleted for the IS2 terminator and various portions of the lambda chromosome. Analysis of these deletions reveals the following: (a) The lambda tR1 terminator is about 50% efficient. (b) In two deletions sequenced, DNA loss occurred as a result of homologous recombination between a 2- or a 4-base pair repeat. (c) By measuring the ability of lambda N product to suppress the polarity of a gal ochre mutation, we demonstrate that the N utilization site in the lambda pR operon lies between tR1 and cro. (d) The level of Cro repressor synthesized by a single copy prophage is sufficient to repress the cI maintenance promoter, prm, but is inadequate to inhibit pR.

Bacteriophage lambda↗