Formylmethionyl-leucylphenylalanine and the SOS operon in Escherichia coli: a model of host-bacterial interactions.
To determine the biological significance of the existence of highly specific receptors for the bacterial chemotactic peptide formylmethionyl-leucylphenylalanine (fMet-Leu-Phe) on neutrophil leucocytes, we investigated the role of this peptide in bacterial metabolism. The UmuD protein of the Escherichia coli SOS operon was identified as having an N-terminal fMet-Leu-Phe sequence and a recombinant E. coli with the umuD gene on plasmid pSB13 was shown to be an over-producer of both UmuD and fMet-Leu-Phe. Activation of SOS genes in conventional wild-type E. coli (K12) by u.v. light or hydrogen peroxide increased fMet-Leu-Phe production up to 4-fold. A RecA- strain, incapable of SOS activation, was a low basal producer of fMet-Leu-Phe and showed no increased production with u.v. light or oxidant stress. We propose that host phagocytes respond to fMet-Leu-Phe and closely related peptides because they are generated by bacteria under oxidant stress. Increased fMet-Leu-Phe production may signal to the host a change in the organism's biological status from commensal to pathogen because of the invasion into tissues exposing bacteria to high pO2 levels and oxidant stress.
Broom
M F
MF
Department of Experimental Medicine, University of Otago Medical School, Dunedin, New Zealand.
Sherriff
R M
RM
Ferry
D M
DM
Chadwick
V S
VS
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D004259:DNA-Directed DNA Polymerase; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015870:Gene Expression / Q000187:drug effects; D006861:Hydrogen Peroxide; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000737:chemistry* / Q000378:metabolism; D009876:Operon; D011498:Protein Precursors / Q000737:chemistry; D011994:Recombinant Proteins / Q000096:biosynthesis; D013014:SOS Response, Genetics / Q000235:genetics*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006861:Hydrogen Peroxide; D004259:DNA-Directed DNA Polymerase; C055218:UmuD protein, E coli