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J. Bacteriol., 11 1995, 6144-6152, Vol 177, No. 21
E Wagner, S Marcandier, O Egeter, J Deutscher, F Gotz and R Bruckner
By transposon Tn917 mutagenesis, 16 mutants of Staphylococcus xylosus were
isolated that showed higher levels of beta-galactosidase activity in the
presence of glucose than the wild-type strain. The transposons were found
to reside in three adjacent locations in the genome of S. xylosus. The
nucleotide sequence of the chromosomal fragment affected by the Tn917
insertions yielded an open reading frame encoding a protein with a size of
328 amino acids with a high level of similarity to glucose kinase from
Streptomyces coelicolor. Weaker similarity was also found to bacterial
fructokinases and xylose repressors of gram- positive bacteria. The gene
was designated glkA. Immediately downstream of glkA, two open reading
frames were present whose deduced gene products showed no obvious
similarity to known proteins. Measurements of catabolic enzyme activities
in the mutant strains grown in the presence or absence of sugars
established the pleiotropic nature of the mutations. Besides
beta-galactosidase activity, which had been used to detect the mutants, six
other tested enzymes were partially relieved from repression by glucose.
Reduction of fructose-mediated catabolite repression was observed for some
of the enzyme activities. Glucose transport and ATP-dependent
phosphorylation of HPr, the phosphocarrier of the
phosphoenolpyruvate:carbohydrate phosphotransferase system involved in
catabolite repression in gram-positive bacteria, were not affected. The
cloned glkA gene fully restored catabolite repression in the mutant strains
in trans. Loss of GlkA function is thus responsible for the partial relief
from catabolite repression. Glucose kinase activity in the mutants reached
about 75% of the wild-type level, indicating the presence of another enzyme
in S. xylosus.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Glucose kinase-dependent catabolite repression in Staphylococcus xylosus
Mikrobielle Genetik, Universitat Tubingen, Germany.
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