The qa repressor gene of XXXX : wild-type and mutant nucleotide sequences.

@entity1522 @entity535 @entity17131 @entity377 @entity1980 @entity505 @entity1473
The qa-1S gene, one of two regulatory genes in the qa gene cluster of @entity1980 , 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 @entity17131 as a @entity505 source. The @entity377 sequence of the qa-1S gene and its flanking regions has been determined. The deduced coding sequence for the qa-1S protein encodes 918 @entity1522 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 @entity1522 of the qa-1S protein. The mutations in three of the mutants involve @entity535 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 @entity1473 -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.
