Molecular cloning, transcriptional analysis, and nucleotide sequence of lacR, a gene encoding the repressor of the lactose phosphotransferase system of Lactococcus lactis.
The repressor gene (lacR) of the lactose phosphotransferase system of Lactococcus lactis subsp. lactis strain MG1820 has been cloned and characterized. Transcription of lacR, into a 1.2-kilobase monocistronic messenger, is repressed approximately 5-fold during growth on lactose. Nucleotide sequence analysis of the lacR gene showed the presence of an open reading frame of 861 base pairs. The deduced amino acid sequence of LacR is homologous to three Escherichia coli regulatory proteins (DeoR, FucR, and GutR) and includes a N-terminal domain (helix-turn-helix) involved in DNA binding and a C-terminal domain that may be responsible for inducer binding. The in vivo function of LacR has been determined by introducing multiple copies of lacR into L. lactis, under control of its own or the unrelated prtP promoter. Growth rates and lactose phosphotransferase system enzyme activities were measured during growth on lactose and glucose. The presence of lacR on a multicopy plasmid resulted in the decrease of lactose phosphotransferase system activity, whereas only on lactose a decrease (25%) of growth rate was observed. No significant difference in growth rate was observed on glucose, indicating that LacR specifically represses the lactose genes of L. lactis.
van Rooijen
R J
RJ
Department of Biophysical Chemistry, Netherlands Institute for Dairy Research (NIZO), Ede.
de Vos
W M
WM
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D007763:Lac Operon; D013294:Lactococcus lactis / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins; D012097:Repressor Proteins / Q000235:genetics*; D015183:Restriction Mapping; D014158:Transcription, Genetic
D011994:Recombinant Proteins; D012097:Repressor Proteins; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System