Correlation between histidine operon expression and guanosine 5'-diphosphate-3'-diphosphate levels during amino acid downshift in stringent and relaxed strains of Salmonella typhimurium.
We have analyzed the correlation of attenuator-independent expression of the Salmonella typhimurium histidine operon in vivo with levels of the "alarmone" guanosine 5'-diphosphate 3'-diphosphate. Amino acid downshift caused by serine hydroxamate addition increased his expression in a relA+ strain and decreased his expression in a relA mutant, whereas levels of guanosine 5'-diphosphate-3'-diphosphate varied in parallel with the changes in his expression in the two strains. In several experiments, overall variations in his expression ranged from 20- to 60-fold after downshift. The mild downshift allowed growth of the cultures to continue at near-preshift rates. Serine hydroxamate addition was also used to analyze the effect of amino acid downshift on induced expression of wild-type and mutant lac promoters. There was a 12-fold difference in lac expression when a relA+-relA1 pair was subjected to mild starvation but only a 3-fold difference when the strains carried the lacZpL8UV5 promoter mutation. These results suggest that guanosine 5'-diphosphate-3'-diphosphate stimulates gene expression in vivo at the level of transcription initiation.
Shand
R F
RF
Department of Microbiology, University of California, Davis 95616.
Blum
P H
PH
Mueller
R D
RD
Riggs
D L
DL
Artz
S W
SW
D000596:Amino Acids / Q000378:metabolism*; D005838:Genotype; D006150:Guanine Nucleotides / Q000378:metabolism*; D006159:Guanosine Tetraphosphate / Q000378:metabolism*; D006639:Histidine / Q000096:biosynthesis*; D007700:Kinetics; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D012694:Serine / Q000031:analogs & derivatives / Q000494:pharmacology; D013045:Species Specificity
D000596:Amino Acids; D006150:Guanine Nucleotides; C028002:serine hydroxamate; D006159:Guanosine Tetraphosphate; D012694:Serine; D006639:Histidine