title: New amino acid regulatory locus having unusual properties in heterozygous merodiploids.
abstract: Spontaneous mutants of Escherichia coli B/r resistant to 5',5',5',-trifluoro-dl-leucine contain defects in a gene which maps to the left of the threonine region. Low-level constitutive expression of the isoleucine-valine and leucine operons is caused by this mutation in haploid strains. This is in contrast to extremely high levels of gene expression in the heterozygous merodiploids (F' wild type/mutant allele). The properties of these mutants define a new locus and suggest that it encodes a subunit protein which is involved in the repression of the structural genes for the branched-chain amino acid pathways.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000483:Alleles; D000596:Amino Acids / Q000096:biosynthesis*; D002474:Cell-Free System; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003470:Culture Media; D003998:Dicarboxylic Acids; D004171:Diploidy; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D005461:Fluorine / Q000494:pharmacology; D005796:Genes; D006579:Heterozygote; D006836:Hydro-Lyases / Q000378:metabolism; D007930:Leucine / Q000494:pharmacology; D008190:Lyases / Q000378:metabolism; D009154:Mutation; D011773:Pyruvates; D011995:Recombination, Genetic; D013912:Threonine; D014161:Transduction, Genetic; D014631:Valerates
chemical_list: D000596:Amino Acids; D003470:Culture Media; D003998:Dicarboxylic Acids; D011773:Pyruvates; D014631:Valerates; D005461:Fluorine; D013912:Threonine; D000217:Acyltransferases; D008190:Lyases; D006836:Hydro-Lyases; D007930:Leucine