title: The qa repressor gene of Neurospora crassa: wild-type and mutant nucleotide sequences.
abstract: The qa-1S gene, one of two regulatory genes in the qa gene cluster of Neurospora crassa, encodes the qa repressor. The qa-1S gene together with the qa-1F gene, which encodes the qa activator protein, control the expression of all seven qa genes, including those encoding the inducible enzymes responsible for the utilization of quinic acid as a carbon source. The nucleotide sequence of the qa-1S gene and its flanking regions has been determined. The deduced coding sequence for the qa-1S protein encodes 918 amino acids with a calculated molecular weight of 100,650 and is interrupted by a single 66-base-pair intervening sequence. Both constitutive and noninducible mutants occur in the qa-1S gene and two different mutations of each type have been cloned and sequenced. All four mutations occur within the predicted coding region of the qa-1S gene. This result strongly supports the hypothesis that the qa-1S gene encodes a repressor. All four mutations are located within codons for the last 300 amino acids of the qa-1S protein. The mutations in three of the mutants involve amino acid substitutions, while the fourth mutant, which has a constitutive phenotype, contains a frameshift mutation. The two constitutive mutations occur in the most distal region of the gene, possibly implicating the COOH-terminal region of the qa repressor in binding to its target. The two noninducible mutations occur in a region proximal to the constitutive mutations, possibly implicating this region of the qa repressor in binding the inducer.
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004720:Endonucleases; D005656:Fungal Proteins / Q000235:genetics; D005800:Genes, Fungal; D005809:Genes, Regulator; D008970:Molecular Weight; D009154:Mutation; D009491:Neurospora / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics*; D011110:Polymorphism, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D005656:Fungal Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D004720:Endonucleases; D015719:Single-Strand Specific DNA and RNA Endonucleases