Fig. 3: 4-CPA structure and transport cycle.

a, Close-up view (left) and cut-away view of surface presentation (right) of the asymmetric PIN8 structure bound 4-CPA in the prebinding state of the inward monomer. b, Close-up view (left) and cut-away view of surface presentation (right) of the symmetric PIN8 structure bound 4-CPA in the binding state of the outward monomer. c, Close-up view (left) and cut-away view of surface presentation (right) of the asymmetric PIN8 structure bound 4-CPA in the partly release state of the outward monomer. Residues belonging to the transporter domain highlighted in light violet and the scaffold domain in violet. Ligands are coloured orange. d, Overlay of 4-CPA prebinding position (PDB 9G0X and EMD-50951) in the inward monomer. The inward-facing pocket is divided into the binding chamber (light violet) and a vestibule (grey). The red broken line running from Asn117 to Asn223 defines the boundary between vestibule to binding chamber. e, Overlay of 4-CPA binding (PDB 9G0Z and EMD-50952) and partly released (PDB 9G10 and EMD-50953) position in the outward monomer. Both structures are superposed on the scaffold domain. The superposition shows that in either state, Asn117 retains its interaction with carboxyl and arylether groups. The planes define the position of the ring systems of NPA, IAA and 4-CPA within the vestibule and binding chamber in the inward monomer and outward facing monomer. Figure created with PyMOL v5.0.4, Molecular Graphics System (Schrödinger, LLC).