Sequences involved in growth-phase-dependent expression and glucose repression of a Streptomyces alpha-amylase gene.
In glycerol-grown, but not in glucose-grown cultures, expression in Streptomyces lividans TK24 of the cloned alpha-amylase gene (aml) of Streptomyces limosus is switched on toward the end of exponential growth. During this period, aml expression is further inducible by maltotriose. We showed that a 378 bp fragment, extending from position -204 through to +174 (relative to the transcriptional start site), included cis-acting sequences involved in aml regulation. When this fragment was present on a multicopy plasmid, the growth-phase-dependent aml expression conferred by a DNA fragment cloned on a compatible low-copy-number plasmid was greatly enhanced, as if negative regulators were being titrated. A study of the regulation of aml expression in variants with deletions in the aml promoter region indicated that a direct repeat (DR) between positions -124 and -106 (relative to the transcriptional start site) and an inverted repeat (IR) between positions +9 and +24 were good candidates for secondary and primary operator sites, respectively. Deletion of a 29 bp fragment containing the IR rendered aml expression partly growth-phase-independent, resistant to glucose repression, and insensitive to maltotriose induction.
Institut de Génétique et Microbiologie, URA CNRS 1354, Université Paris-Sud, Orsay, France.
M J
MJ
Virolle
J
J
Gagnat
D000595:Amino Acid Sequence; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004794:Enzyme Repression / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005822:Genetic Vectors / Q000235:genetics; D005947:Glucose / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011994:Recombinant Proteins; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D017384:Sequence Deletion; D013302:Streptomyces / Q000235:genetics* / Q000254:growth & development; D014158:Transcription, Genetic; D014312:Trisaccharides / Q000494:pharmacology; D000516:alpha-Amylases / Q000096:biosynthesis* / Q000235:genetics
D011994:Recombinant Proteins; D014312:Trisaccharides; C008317:maltotriose; D000516:alpha-Amylases; D005947:Glucose