Isolation of atrans-Dominant Histidase-Negative Mutant ofSalmonella typhimurium

Abstract

A mutation of Salmonella typhimurium was obtained that results in the failure of cells to synthesize the enzyme L-histidine ammonia-lyase (histidase). The mutation mapped within the hutH gene and in merodiploid strains was dominant over the wild-type allele. Extracts from cells bearing the trans-dominant histidase-negative allele were shown to contain material that reacts immunologically with antiserum against purified wild-type histidase. It is proposed that the transdominant allele results in the synthesis of defective histidase subunits that can combine with, and partially inactivate, wild-type histidase subunits. This subunit mixing presumably does occur, as the enzyme synthesized in a hybrid merodiploid strain is abnormally heat sensitive.

Genetic and physical maps of Klebsiella aerogenes genes for histidine utilization (hut)

“…About 1 Kb has been allowed for the four structural genes and a little over 0.5 Kb for the hutC gene. This is consistent with the size of the products of the hutG, U and H genes from other organisms (Hagen et al 1974;Magasanik et al 1971). Our K. aerogenes map is similar to the map of hut from S. t'yphimurium.…”

“…The data in Table 3 show clearly that the deletion in pCBI02 interrupts the hutH gene, but the ability of pCB102 expression to interfere with chromosomal hutH-encoded histidase activity strongly resembles the trans-dominant hutH mutation described by Hagen et al (1974). This would predict that a portion of hutH remains and that the polypeptide produced by this fusion of hutH sequences with "foreign" DNA sufficiently resembles the histidase polypeptide to co-assemble with normal histidase subunits resuiting in an inactive histidase multimer.…”

Isolation of super-repressor mutants in the histidine utilization system of Salmonella typhimurium

“…Other mutants obtained in the selection for growth of NE645 on succinate-ammonia minimal medium plus 1% histidine at 43 C included: mutants bearing hutH-(or hutU-) on both the episome and the chromosome (derived, presumably, from a single mutational event followed by homogenotization); and mutants bearing transdominant hutHmutations (see reference 4 and Discussion).…”

“…Both procedures have been published (9,11). Prospective hut-negative mutations were analyzed by a replica-plating complementation test (4).…”

The genetics ofSleek: a possible regulatory mutation of thetabby-crinkled-downlesssyndrome

“…If the dl allele were to produce none of the protein the homozygote would be mutant but the heterozygote would still have half the concentration of active product and therefore would appear normal. Such a model has already been proposed to explain the behaviour of mutations at the histidase structural locus (hut H) of Salmonella (Hagen, Lipton & Magasanik, 1974).…”