Fig. 1: 2,4-D is a PIN substrate.
From: Transport of phenoxyacetic acid herbicides by PIN-FORMED auxin transporters
a, Peak current response as a function of the concentrations of IAA (filled triangles) and 2,4-D (filled circles) determined by SSM electrophysiology on PIN8 proteoliposomes. A Michaelis–Menten model is fit to describe kinetics (\({r}_{\rm{IAA}}^{2}\) = 0.9579; \({\rm{EC}}_{50}^{\rm{IAA}}\) = 254 ± 6 μM; \({I}_{\max }^{\rm{IAA}}\) = 18 ± 3 nA versus \({r}_{\mathrm{2,4}{\mbox{-}}{\rm{D}}}^{2}\) = 0.9802; \({\rm{EC}}_{50}^{\mathrm{2,4}{\mbox{-}}{\rm{D}}}\) = 179 ± 10 μM; \({I}_{\max }^{\mathrm{2,4}{\mbox{-}}{\rm{D}}}\) = 17 ± 2 nA; data points represent mean ± s.e.m.; n = 4 individual sensors). Inset: peak current response elicited by 100 μM 2,4-D in the absence or presence of 20 µM NPA. Data are mean ± s.e.m. of n = 3 individual sensors. Groups were compared by a two-sided unpaired Student’s t-test. *P = 0.0126. b, Relative transport rates of [3H]-2,4-D export by PIN8 in the presence or absence of 10 μM NPA as indicated from oocytes calculated from four independent time course experiments. Data points are individual experiments, and bars represent mean ± s.d. Groups were compared by a two-sided unpaired Student’s t-test. *P = 0.0361; n = 4 individual experiments. c, Relative transport rates of [3H]-2,4-D export by PIN3 with or without the activating PID kinase in the presence or absence of 10 μM NPA as indicated from oocytes calculated from three independent time course experiments. Data points are individual experiments, and bars represent mean ± s.d. Groups were compared by a two-sided unpaired Student’s t-test. NS, not significant P = 0.6411; **P = 0.0004; n = 3 individual experiments. d, Structure of asymmetric dimeric PIN8 with 2,4-D bound to the inward open monomer in a prebinding position in the vestibule (right panel). The transporter domain is highlighted in light violet and the scaffold domain in violet, and the ligand is coloured orange. Close-up view of 2,4-D and the residues from the scaffold domain (violet) and transporter domain (light violet) interacting with the substrate. The inward-open pocket is divided into the binding chamber (highlight in light orange) and a vestibule (highlight in grey). Red spheres represent water molecules. Figure created with PyMOL v5.0.4, Molecular Graphics System (Schrödinger, LLC).
