Glucose repression in Streptomyces coelicolor A3(2): a likely regulatory role for glucose kinase.
The glucose kinase gene (glkA-ORF3) of Streptomyces coelicolor A3(2) plays an essential role in glucose utilisation and in glucose repression of a variety of genes involved in the utilisation of alternative carbon sources. These genes include dagA, which encodes an extracellular agarase that permits agar utilisation. Suppressor mutants of glkA-ORF3 deletion strains capable of utilising glucose (Glc+) arise at a frequency of about 10(-5) on prolonged incubation. The Glc+ phenotype of the mutants is reversible (at a frequency of about 10(-3) and reflects either the activation of a normally silent glucose kinase gene or the modification of an existing sugar kinase. Although the level of glucose kinase activity in the Glc+ supressor mutants is similar to that in the glkA+ parental strain, glucose repression of dagA remains defective. Expression of the glucose kinase gene of Zymomonas mobilis in glkA-ORF3 mutants restored glucose utilisation, but not glucose repression of dagA. Over-expression of glkA-ORF3 on a high-copy-number plasmid failed to restore glucose repression of dagA in glkA-ORF3 mutants and led to loss of glucose repression of dagA in a glkA+ strain. These results suggest that glucose phosphorylation itself is not sufficient for glucose repression and that glkA-ORF3 plays a specific regulatory role in triggering glucose repression in S. coelicolor A3(2).
Angell
S
S
John Innes Centre, Colney, Norwich, UK.
Lewis
C G
CG
Buttner
M J
MJ
Bibb
M J
MJ
D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000032:analysis / Q000378:metabolism; D004794:Enzyme Repression; D005798:Genes, Bacterial; D005838:Genotype; D005941:Glucokinase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D016366:Open Reading Frames; D010641:Phenotype; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013302:Streptomyces / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D017355:Zymomonas
D004269:DNA, Bacterial; D011994:Recombinant Proteins; D005941:Glucokinase; D005947:Glucose