title: Control of expression of the pyr genes in Salmonella typhimurium: effects of variations in uridine and cytidine nucleotide pools.
abstract: The differential rate of synthesis of five of the pyrimidine biosynthetic enzymes coded for by pyrB-F, and the endogenous concentrations of the individual pyrimidine nucleotides were determined in specially constructed mutants of Salmonella typhimurium. In the mutants employed the different pyrimidine nucleotide pools may be manipulated individually during exponential growth. The results obtained indicate the following. (i) The expression of pyrB, pyrE, and pyrF is controlled by a uridine nucleotide in a noncoordinate manner. (ii) The expression of pyrC and pyrD is regulated predominantly by a cytidine nucleotide. Under all conditions investigated, their expression seems to be coordinated, even though the genes are not contiguous on the chromosome. (iii) The low-molecular-weight effectors involved in controlling the expression of the pyr genes are neither uridine 5'-monophosphate nor cytidine 5'-monophosphate, but rather the corresponding di- or triphosphates.
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D001221:Aspartate Carbamoyltransferase / Q000378:metabolism; D002262:Carboxy-Lyases / Q000378:metabolism; D002474:Cell-Free System; D002874:Chromosome Mapping; D003545:Cysteine / Q000378:metabolism; D003562:Cytidine / Q000378:metabolism; D003597:Cytosine Nucleotides / Q000378:metabolism*; D004794:Enzyme Repression; D005796:Genes; D008040:Genetic Linkage; D009154:Mutation; D009963:Orotic Acid; D010088:Oxidoreductases / Q000378:metabolism; D010430:Pentosyltransferases / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D011742:Pyrimidine Nucleotides / Q000096:biosynthesis*; D012486:Salmonella typhimurium / Q000201:enzymology / Q000378:metabolism*; D014161:Transduction, Genetic; D014498:Uracil / Q000378:metabolism; D014500:Uracil Nucleotides / Q000378:metabolism*
chemical_list: D003597:Cytosine Nucleotides; D011742:Pyrimidine Nucleotides; D014500:Uracil Nucleotides; D014498:Uracil; D003562:Cytidine; D009963:Orotic Acid; D001120:Arginine; D010088:Oxidoreductases; D001221:Aspartate Carbamoyltransferase; D010430:Pentosyltransferases; D010770:Phosphotransferases; D000581:Amidohydrolases; D002262:Carboxy-Lyases; D003545:Cysteine