Fig. 1
Fpr3 detects signal sequences from bacterial virulence-associated proteins. a Heterologous expression and high-throughput agonist screening reveals exquisite selectivity of Fpr3. Bars denote mean Ca2+ responses of Fpr3-transfected HEK293T cells to one of 41 different bacterial signal peptide sequences, at 3 or 30 µM. f-MKKFRW (mellow yellow) caused Fpr3 activation, but all other tested peptides (grey bars) did not. Numbers above each bar indicate the number of independent experiments, each one carried out in triplicates. The dashed line denotes the negative control signal obtained from application of assay buffer without an added peptide (black bars, mock). Amino acid sequences of the 6–9 residue-long peptides are displayed in one-letter code; (f-) indicates a formylation of the N-terminal methionine. Error bars indicate standard deviations (s.d.). b–e Bioinformatic analyses of MKKFRW-containing proteins as annotated in UniProt. Numbers in parentheses indicate the number of database entries. b Distribution of MKKFRW-containing proteins in different organisms. c Location of the MKKFRW motif within a given protein from all 392 UniProt entries found in bacteria. d Distribution of the MKKFRW motif between Gram-positive and Gram-negative bacteria. e Distribution of proteins that contain the MKKFRW motif. f, g Pathogenicity potential of mgrB+ bacterial strains. f Biosafety level classification of mgrB+ bacterial strains. Risk group 3, red; risk group 2, yellow; risk group 1, green; non-annotated strains, white. Numbers in parentheses indicate number of strains found in each genus (right panel). g The mgrB+ list comprises various obligate pathogenic E. coli variants such as enterohemorrhagic E. coli (EHEC), Shiga toxin producing E. coli (STEC), uropathogenic E. coli (UPEC), enterotoxigenic E. coli (ETEC), extraintestinal pathogenic E. coli (ExPEC), enteroaggregative E. coli (EAEC), enterophathogenic E. coli (EPEC), or adherent invasive E. coli (AIEC) that are listed as risk group 2 and 3 (EHEC) organisms, respectively. Source data are provided as a Source Data file
