Interaction between phosphoribosyltransferase and purified histidine tRNA from wild type Salmonella typhimurium and a derepressed hisT mutant strain

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Abstract
We have examined the interaction between phosphoribosyltransferase and purified tRNAHis from the wild type strain of Salmonella typhimurium, LT-2, and the histidine regulatory mutant hisT1504. Histidylt-RNA from the mutant strain functions normally in protein synthesis but is defective in its role in the repression mechanism of the histidine operon. Phosphoribosyltransferase has been suggested as a possible aporegulator for this operon and as such might be expected to interact abnormally with tRNAHis from hisT1504. In these studies we have been unable to detect any difference between the affinities of phosphoribosyltransferase for tRNAHis from LT-2 or hisT1504, and thus we conclude that if the complex between phosphoribosyltransferase and histidyl-tRNA does function in regulation, the defect in the hisT1504 mutant must influence the interaction of the complex with some other regulatory element.