title: TolC-dependent exclusion of porphyrins in Escherichia coli.
abstract: We found that Escherichia coli tolC mutants showed increased sensitivity to 5-aminolevulinic acid (ALA), a precursor of porphyrins. The tolC mutant cells grown in the presence of ALA showed a reddish brown color under visible light and a strong red fluorescence under near-UV irradiation. Fluorescence spectrometry and high-performance liquid chromatography analysis showed that the tolC mutant cells grown in the presence of ALA accumulated a large amount of coproporphyrin(ogen) intracellularly. In contrast, the wild-type cells produced coproporphyrin extracellularly. The tolC mutant cells grown in the presence of ALA, which were capable of surviving in the dark, were killed by near-UV irradiation, suggesting that the intracellular coproporphyrin(ogen) renders these cells photosensitive. These results suggest that the TolC-dependent efflux system is involved in the exclusion of porphyrin(ogen)s in E. coli.
authors.affiliation: Department of Bioengineering, Tokyo Institute of Technology, 4259-J2-14 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Tatsumi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Wachi
mesh_terms: D000622:Aminolevulinic Acid / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011166:Porphyrins / Q000737:chemistry / Q000378:metabolism*; D011836:Radiation Tolerance
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011166:Porphyrins; C073126:tolC protein, E coli; D000622:Aminolevulinic Acid