Leucine-responsive regulatory protein controls the expression of both the pap and fan pili operons in Escherichia coli.
The methylation blocking factor gene (mbf) in Escherichia coli is required for specific methylation inhibition of two DNA GATC sites upstream of the papBA pilin promoter and transcriptional activation of pap. Complementation and mutational analysis using pap-lac and ilvIH-lac operon fusions indicates that the mbf gene is identical to a recently described global regulatory gene lrp (leucine-responsive regulatory protein) that acts as a positive regulator of some genes and a negative regulator of others in E. coli. DNA sequence analysis of an mbf::mTn10 insertion showed that the mbfDNA sequence was identical to lrp. Thus Lrp inhibits DNA methylation at specific GATC sites. We also show that Lrp positively regulates transcription of the fan operon, which encodes K99 pili of diarrheagenic E. coli. Purified Lrp was found to bind to DNA fragments encompassing the pap and fan promoters, which is consistent with previous results indicating that Lrp controls gene expression by binding to regulatory DNA sites. Exogenous leucine significantly reduced fan transcription and K99 pili expression, similar to results obtained with the ilvIH operon. However, pap gene expression was unresponsive to leucine, which distinguishes pap from other lrp-regulated genes whose expression is modulated by leucine.
Department of Pathology, University of Utah Medical Center, Salt Lake City 84132.
B A
BA
Braaten
J V
JV
Platko
M W
MW
van der Woude
B H
BH
Simons
F K
FK
de Graaf
J M
JM
Calvo
D A
DA
Low
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D007930:Leucine / Q000494:pharmacology; D051756:Leucine-Responsive Regulatory Protein; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009838:Oligodeoxyribonucleotides; D009876:Operon; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000187:drug effects
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D014157:Transcription Factors; D051756:Leucine-Responsive Regulatory Protein; D007930:Leucine