Identification of the lrp gene in Bradyrhizobium japonicum and its role in regulation of delta-aminolevulinic acid uptake.
The heme precursor delta-aminolevulinic acid (ALA) is taken up by the dipeptide permease (Dpp) system in Escherichia coli. In this study, we identified a Bradyrhizobium japonicum genomic library clone that complemented both ALA and dipeptide uptake activities in E. coli dpp mutants. The complementing B. japonicum DNA encoded a product with 58% identity to the E. coli global transcriptional regulator Lrp (leucine-responsive regulatory protein), implying the presence of Dpp-independent ALA uptake activity in those cells. Data support the conclusion that the Lrp homolog induced the oligopeptide permease system in the complemented cells by interfering with the repressor activity of the endogenous Lrp, thus conferring oligopeptide and ALA uptake activities. ALA uptake by B. japonicum was effectively inhibited by a tripeptide and, to a lesser extent, by a dipeptide, and a mutant strain that expressed the lrp homolog from a constitutive promoter was deficient in ALA uptake activity. The data show that Lrp negatively affects ALA uptake in E. coli and B. japonicum. Furthermore, the product of the isolated B. japonicum gene is both a functional and structural homolog of E. coli Lrp, and thus the regulator is not restricted to enteric bacteria.
King
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ND
Department of Biochemistry, Center for Advanced Molecular Biology and Immunology, State University of New York at Buffalo, 14214, USA.
O'Brian
M R
MR
D000595:Amino Acid Sequence; D000622:Aminolevulinic Acid / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D051756:Leucine-Responsive Regulatory Protein; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D012230:Rhizobiaceae / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors; D014169:Transformation, Bacterial
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004151:Dipeptides; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; D026901:Membrane Transport Proteins; D009842:Oligopeptides; D014157:Transcription Factors; D051756:Leucine-Responsive Regulatory Protein; C037230:oligopeptide permease, Bacteria; C057749:prolylglycine; C098153:glycyl-histidyl-glycine; D000622:Aminolevulinic Acid