Inhibition of histidyl-tRNA-adenosine triphosphate phosphoribosyltransferase complex formation by histidine and by guanosine tetraphosphate.

Formation of the complex between the first enzyme of histidine biosynthesis from Salmonella typhimurium, ATP phosphoribosyltransferase [1-(5'-phosphoribosyl)-ATP: pyrophosphate phosphoribosyltransferase; EC 2.4.2.17], and histidyl-tRNA is shown to be inhibited by L-histidine and by guanosine-5'-diphosphate-3'-diphosphate in the presence of histidine. Higher histodine levels make guanosine tetraphosphate a more effective inhibitor. Relatively high concentrations of guanosine-5'-triphosphate also inhibit complex formation, but this inhibition is not enhanced by histidine. The possible implications of these observations with respect to the gene regulatory activity of this enzyme are discussed.