Identification and characterization of the ilvR gene encoding a LysR-type regulator of Caulobacter crescentus.
The ilvR gene was located upstream of and transcribed divergently from the ilvD gene of Caulobacter crescentus. DNA nucleotide analysis determined that the ilvR and ilvD translation initiation codons are 98 bp apart. The promoter activity of the DNA region containing the divergent promoters was analyzed by using transcriptional fusions to promoterless reporter genes and immunoblot assays. The results indicate that the ilvR gene product positively regulates the expression of the ilvD gene while negatively autoregulating its own expression. The ilvR gene codes for a protein of 296 amino acid residues (M(r), 37,212). The N-terminal amino acid sequence of the IlvR protein contains a helix-turn-helix motif, suggesting that it is involved in protein-DNA interactions. Protein extracts from both wild-type and merodiploid strains showed specific DNA binding to a 227-bp DNA fragment spanning the ilvD-ilvR promoter region, while no protein-DNA complexes were observed in cell extracts from an ilvR mutant strain. Amino acid sequence comparison revealed that the IlvR protein is a member of the LysR family of transcriptional regulators.
Malakooti
J
J
Department of Biological Sciences, University of South Carolina, Columbia 29208.
Ely
B
B
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015139:Blotting, Southern; D016935:Caulobacter crescentus / Q000235:genetics* / Q000378:metabolism; D002876:Chromosomes, Bacterial; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D014157:Transcription Factors; C086033:ilvR protein, Caulobacter crescentus; C073470:LysR protein, Bacteria