ACTION OF A HISTIDINE ANALOGUE, 1,2,4-TRIAZOLE-3-ALANINE, IN SALMONELLA TYPHIMURIUM

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Abstract
The effect of the histidine analogue, l,2,4-triazole-3-alanine (TRA), on growth and enzyme synthesis in histidine auxotrophs of Salmonella typhimurium has been studied. TRA allows an increase of approximately 50% in the amount of protein in a culture but does not allow concomitant synthesis of ribonucleic-acid and deoxyribonucleic-acid. Although the analogue prevents the formation of active bacteriophage and of enzymatically active inosine monophosphate dehydrogenase, it does not prevent the formation of enzymatically active L-histidinol phosphate phosphatase or of imidazoleacetol phosphate transaminase-two enzymes involved in the biosynthesis of histidine. Of the three known functions of histidine in the cell, TRA mimics two it is incorporated into protein, and it acts as a repressor material for synthesis of enzymes involved in the formation of histidine. TRA fails to act as a feedback inhibitor of the first step in the formation of histidine.