Fig 1. Synthesis and detection of DSF AIs.
(A) Structure of DSF (cis-2-11-methyl-dodecenoic acid), BDSF (cis-2-dodecenoic acid), and PDSF (cis-2-decenoic acid). (B) RpfF synthesizes BDSF in a two-step mechanism. RpfF dehydrates 3-hydroxydodecanoyl-ACP to form the cis-2-dodecenoyl-ACP. RpfF hydrolyzes the thioester bond linking the acyl-chain to ACP, releasing holo-ACP and free BDSF. (C) Schematic representation of RpfR. (Top) The genomic orientation of rpfF and rpfR show that they are convergently transcribed. (Bottom) A schematic representation of RpfRCt. The FI domain (residues 1–95) and PAS domain (residues 118–224) are depicted in blue and yellow, respectively. The approximate positions of the DGC and PDE domains (gray) were determined by sequence homology. Linker regions between domains are shown in white. (D) Previously established BDSF-signaling model. (Left panel) At low levels of BDSF, RpfR PDE activity is low and c-di-GMP levels are high. (Right panel) At elevated concentrations, BDSF binds to the RpfR PAS domain, triggering RpfR PDE-mediated hydrolysis of c-di-GMP to pGpG. ACP, acyl carrier protein; AI, autoinducer; BDSF, Burkholderia DSF; c-di-GMP, bis-(3′-5′)-cyclic dimeric guanosine monophosphate; DGC, diguanylate cyclase; DSF, diffusible signal factor; FI, RpfF interaction; PAS, Per-Arnt-Sim; PDE, phosphodiesterase; PDSF, Pseudomonas DSF; pGpG, 5′-phosphoguanylyl-(3′,5′)-guanosine; RpfF, regulation of pathogenicity factor F; RpfR, regulation of pathogenicity factor R.