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. 2025 Aug 4;11(8):1670–1680. doi: 10.1038/s41477-025-02056-z

Fig. 1. Activity and structural overview of LAX3.

Fig. 1

a, Kinetics of LAX3-mediated IAA uptake into Xenopus oocytes. Uptake can be described by a Michaelis–Menten model (r2 = 0.93, Km = 218 ± 51 nM, Vmax = 35 ± 19 fmol min−1 per oocyte). Data are presented as mean values ± s.e.m. Points represent rates derived from biologically independent time-course measurements, with raw data shown in Extended Data Fig. 3a (n = 5). b, The impact of inhibitors and competitors on LAX3-mediated IAA uptake into Xenopus oocytes at [3H-IAA] = 100 nM. Uptake of LAX3-injected oocytes in the presence of 10 µM IAA, 2,4-D, 1-NOA, 2-NOA or 1 µM of the proton decouplers 2,4-dinitrophenol (2,4-DNP) or carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP). Each data point represents the uptake of one individual oocyte. The error bars show the mean ± s.e.m, n = 20 except [3H]-IAA where n = 19. One-way analysis of variance (ANOVA) followed by Dunnett’s multiple-comparisons test was used for data analysis. P values: [3H-IAA] versus [3H-IAA] + IAA: P = 0.0077, [3H-IAA] versus [3H-IAA] + 2,4-D: P = 0.0002, [3H-IAA] versus [3H-IAA] + 1-NOA: P = 0.0022, [3H-IAA] versus [3H-IAA] + 2-NOA: P = 0.0015, [3H-IAA] versus [3H-IAA] + 2,4-DNP: P = 0.0484, [3H-IAA] versus [3H-IAA] + FCCP: P = 0.9962. For uncorrected data, see Extended Data Fig. 3d. c, Topology diagram of LAX3 containing two APC transporter repeats (1 and 2), each comprising five transmembrane helices. The bundle domain (green) consisting of M1, M3, M6 and M8, and the scaffold domain (light purple) with M2, M4, M5, M7 and M9, form the core of the transporter. In addition, the transporter has two arms, M5 and M10 (orange), and an extra C-terminal helix, M11 (white), which breaks the internal symmetry of the transporter. d, The cryo-EM electrostatic potential map of the 3.21 Å structure of LAX3 bound to IAA, with colour coding as in c. e, A cartoon presentation of the LAX3 IAA-bound structure. The IAA-binding site is situated between the scaffold domain and the bundle domain and is highlighted with the chemical structure of IAA shown in orange. f, Top view of LAX3 seen from the cytosolic side, 90° rotation relative to e. The IAA binding site is highlighted as in e.