title: D-Fucose as a gratuitous inducer of the L-arabinose operon in strains of Escherichia coli B-r mutant in gene araC.
abstract: d-Fucose, a nonmetabolizable analogue of l-arabinose, prevents growth of Escherichia coli B/r on a mineral salts medium plus l-arabinose by inhibiting induction of the l-arabinose operon. Mutations giving rise to d-fucose resistance map in gene araC and result in constitutive expression of the l-arabinose operon. Most of these mutations also permit d-fucose to serve as a gratuitous inducer. It is concluded that d-fucose-resistant mutants produce an araC gene product with an altered inducer specificity. Addition of l-arabinose to cells induced with the gratuitous inducer, d-fucose, resulted in severe transient repression of operon expression followed by permanent catabolite repression. Transient repression but no permanent catabolite repression was obtained when cells unable to metabolize l-arabinose were employed. It is concluded that transport of l-arabinose alone is sufficient to achieve transient repression of its own operon, but that metabolism of l-arabinose must occur to achieve permanent catabolite repression of the l-arabinose operon. This general effect has been termed "self-catabolite repression."
mesh_terms: D001089:Arabinose / Q000378:metabolism* / Q000494:pharmacology; D002474:Cell-Free System; D002874:Chromosome Mapping; D003470:Culture Media; D004171:Diploidy; D004352:Drug Resistance, Microbial; D004790:Enzyme Induction; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D005643:Fucose / Q000494:pharmacology*; D005796:Genes; D005827:Genetics, Microbial; D007535:Isomerases / Q000096:biosynthesis; D009154:Mutation; D013237:Stereoisomerism; D014161:Transduction, Genetic
chemical_list: D003470:Culture Media; D005643:Fucose; D001089:Arabinose; D007535:Isomerases