摘要
The PIN-FORMED (PIN) protein family of auxin transporters mediates the polar auxin transport and plays crucial roles in plant growth and development1,2. Here we present cryo-EM structures of PIN3 from Arabidopsis thaliana (AtPIN3) in the apo state and in complex with its substrate indole-3-acetic acid (IAA) and the inhibitor N-1-naphthylphthalamic acid (NPA) at 2.6-3.0 Å resolution. AtPIN3 exists as a homodimer, with the transmembrane helices (TMs) 1, 2, and 7 in the scaffold domain involved in dimerization. The dimeric AtPIN3 forms a large, joint extracellular-facing cavity at the dimer interface while each subunit adopts an inward-facing conformation. The structural and functional analyses, along with computational studies, reveal the structural basis for the recognition of IAA and NPA and elucidate the molecular mechanism of NPA inhibition on the PIN-mediated auxin transport. The AtPIN3 structures support an elevator-like model for the transport of auxin, whereby the transport domains undergo up-down rigid-body motions and the dimerized scaffold domains remain static.
