Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
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Gene/Protein
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Target Concepts:
Gene/Protein
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Query: EC:3.2.1.23 (
beta-galactosidase
)
14,648
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Mutants of Kluyveromyces lactis with elevated uninduced levels of
beta-galactosidase
(EC 32.1.2.3) activity, constitutive mutants (lac10c), were isolated and characterized to determine the basis for their constitutiveness. These lesions are not operator-type regulatory mutants because they are not closely linked to the
beta-galactosidase
structural gene. In a constitutive strain having a 7-fold increase in
beta-galactosidase
activity, the concentration of
beta-galactosidase
messenger ribonucleic acid (mRNA) was 8- to 10-fold higher than uninduced wild type. The half-life of
beta-galactosidase
mRNA was the same in the mutant strain (t1/2 = 4.5 +/- 0.2 min) as in uninduced wild-type cells (t1/2 = 4.8 +/- 0.1 min), indicating that the elevated mRNA level in the mutant was not due to a decreased rate of mRNA degradation. Consequently, we hypothesize that the LAC10 product regulates transcription of the
beta-galactosidase
gene; it probably affects the rate of transcription initiation. Parallel increases in enzyme protein, in constitutive levels of
beta-galactosidase
activity, and in mRNA further support this position, making translational or posttranslational control by LAC10 unlikely. Several types of data suggest that the LAC10 product functions as a negative regulatory element to prevent transcription. Other data demonstrate that lac10c mutations have pleiotrophic effects, there being constitutive levels not only of
beta-galactosidase
activity, but also the other lactose-inducible activities of galactokinase (EC 2.7.5.1), galactose-1-phosphate uridyl transferase (
EC 2.7.7.10
), and lactose transport. It would appear that LAC10 regulates lactose-inducible proteins.
...
PMID:Genetic regulation: yeast mutants constitutive for beta-galactosidase activity have an increased level of beta-galactosidase messenger ribonucleic acid. 681 93
The Thermus thermophilus TH125 alpha-galactosidase gene, agaT, and flanking sequences were cloned in Escherichia coli and sequenced as well as flanking sequences of the previously cloned agaT from Thermus brockianus ITI360. Different structures of putative alpha-galactosidase operons in the two Thermus strains were revealed. Downstream of and overlapping with the alpha-galactosidase genes of both strains, a gene was identified that is similar to the
galactose-1-phosphate uridylyltransferase
gene (galT) of E. coli and Streptomyces lividans. Upstream of the agaT of T. brockianus ITI360, four open reading frames were observed. The deduced translation products displayed similarity to components of bacterial binding protein-dependent transport systems and a
beta-galactosidase
. No galactoside utilization genes were identified upstream of agaT in T. thermophilus TH125. The inactivation of the alpha-galactosidase genes of both strains by insertional mutagenesis led to an inability to use melibiose or galactose as a single carbohydrate source. An attempt was made to isolate a gene encoding the enzyme responsible for para-nitrophenyl-(pNP-) beta-galactoside hydrolyzing activity in T. thermophilus TH125. A gene designated bglT was cloned and expressed in E. coli. The inactivation of the bglT gene led to 55% reduction of the pNP-beta-galactoside hydrolyzing activity in the mutant strain in comparison to the wild type.
...
PMID:The structure of the alpha-galactosidase gene loci in Thermus brockianus ITI360 and Thermus thermophilus TH125. 1074 34
