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PMID:9603808

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Citation

Bettenbrock, K and Alpert, CA (1998) The gal genes for the Leloir pathway of Lactobacillus casei 64H. Appl. Environ. Microbiol. 64:2013-9

Abstract

The gal genes from the chromosome of Lactobacillus casei 64H were cloned by complementation of the galK2 mutation of Escherichia coli HB101. The pUC19 derivative pKBL1 in one complementation-positive clone contained a 5.8-kb DNA HindIII fragment. Detailed studies with other E. coli K-12 strains indicated that plasmid pKBL1 contains the genes coding for a galactokinase (GalK), a galactose 1-phosphate-uridyltransferase (GalT), and a UDP-galactose 4-epimerase (GalE). In vitro assays demonstrated that the three enzymatic activities are expressed from pKBL1. Sequence analysis revealed that pKBL1 contained two additional genes, one coding for a repressor protein of the LacI-GalR-family and the other coding for an aldose 1-epimerase (mutarotase). The gene order of the L. casei gal operon is galKETRM. Because parts of the gene for the mutarotase as well as the promoter region upstream of galK were not cloned on pKBL1, the regions flanking the HindIII fragment of pKBL1 were amplified by inverse PCR. Northern blot analysis showed that the gal genes constitute an operon that is transcribed from two promoters. The galKp promoter is inducible by galactose in the medium, while galEp constitutes a semiconstitutive promoter located in galK.

Links

PubMed PMC106272

Keywords

Carbohydrate Epimerases/genetics; Carbohydrate Metabolism; Cloning, Molecular; Escherichia coli/genetics; Fermentation; Galactokinase/genetics; Galactose/genetics; Galactose/metabolism; Gene Expression; Genes, Bacterial; Genetic Complementation Test; Lactobacillus casei/genetics; Lactobacillus casei/growth & development; Lactobacillus casei/metabolism; Mutation; Operon; Promoter Regions, Genetic; Repressor Proteins/genetics; UDPglucose 4-Epimerase/genetics; UTP-Hexose-1-Phosphate Uridylyltransferase/genetics

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

LACCA:GAL1

GO:0004335: galactokinase activity

ECO:0000315:

F

Enzymatic assays indicate galK gene is translated into active proteins. Fig 3. shows T7 overexpression of the gal gene products. Fig. 5 shows induction of galK with activity reaching a max after 3 hours.

complete
CACAO 4977


See also

References

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