The pyrimidine operon pyrRPB-carA from Lactococcus lactis.
The four genes pyrR, pyrP, pyrB, and carA were found to constitute an operon in Lactococcus lactis subsp. lactis MG1363. The functions of the different genes were established by mutational analysis. The first gene in the operon is the pyrimidine regulatory gene, pyrR, which is responsible for the regulation of the expression of the pyrimidine biosynthetic genes leading to UMP formation. The second gene encodes a membrane-bound high-affinity uracil permease, required for utilization of exogenous uracil. The last two genes in the operon, pyrB and carA, encode pyrimidine biosynthetic enzymes; aspartate transcarbamoylase (pyrB) is the second enzyme in the pathway, whereas carbamoyl-phosphate synthetase subunit A (carA) is the small subunit of a heterodimeric enzyme, catalyzing the formation of carbamoyl phosphate. The carA gene product is shown to be required for both pyrimidine and arginine biosynthesis. The expression of the pyrimidine biosynthetic genes including the pyrRPB-carA operon is subject to control at the transcriptional level, most probably by an attenuator mechanism in which PyrR acts as the regulatory protein.
Martinussen
J
J
Department of Microbiology, The Technical University of Denmark, DK-2800 Lyngby, Denmark. imjm@pop.dtu.dk
Schallert
J
J
Andersen
B
B
Hammer
K
K
D000595:Amino Acid Sequence; D001221:Aspartate Carbamoyltransferase / Q000096:biosynthesis / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D049308:Dioxygenases; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D009154:Mutation; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D009876:Operon; D010105:Oxygenases / Q000096:biosynthesis / Q000235:genetics*; D010430:Pentosyltransferases / Q000235:genetics*; D011743:Pyrimidines / Q000096:biosynthesis*; D012097:Repressor Proteins / Q000235:genetics*; D016415:Sequence Alignment; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D011743:Pyrimidines; D012097:Repressor Proteins; D010105:Oxygenases; D049308:Dioxygenases; C108434:carbazole 1,9a-dioxygenase; D001221:Aspartate Carbamoyltransferase; D010430:Pentosyltransferases; C098851:PyrR protein, bacteria; C030986:pyrimidine