Fig. 1.

The Pseudomonas GM79 pipR genomic region, HEHEAA chemical structure, AapF activity analysis, and structure of SBP_PDC86-HEHEAA complex. (A) The pipR (green) genomic region. Genes coding for the predicted ABC-type transporter are in red, and genes coding for peptidases are in blue. (B) Chemical structure of HEHEAA with the ethanolamine (EA) and glycine (Gly) substructures indicated. (C) SBP_PDC86, but not SBP_DC3000, can substitute for SBP_GM79. Data are pipA-gfp fluorescence in a GM79 aapF mutant harboring plasmids with the indicated aapF gene and a pipA-gfp reporter. Cells were grown with (black bars) or without (white bars) 100 nM HEHEAA. The pipA-gfp expression is in relative fluorescence units (RFU) per optical density (OD₆₀₀) of four biological replicates, and the error bars represent the SDs of the mean. (D) Ribbon diagram of the overall structure of SBP_PDC86-HEHEAA complex. The three domains I_a, I_b, and II are labeled and colored in sky blue, gray blue, and green, respectively. β-strands and α-helices are labeled with numbers and letters, respectively. The ligand HEHEAA is shown as ball-and-stick model in magenta. (E) Surface representation of SBP_PDC86 with the same color scheme as in D. The HEHEAA ligand is completely buried inside the structure. The structure figures were produced with PyMOL (www.pymol.org).