8i3a | pdb_00008i3a
Cryo-EM structure of abscisic acid transporter AtABCG25 in outward conformation
Structural highlights
FunctionAB25G_ARATH High affinity abscisic acid (ABA) transporter that mediates the export of ABA, with a preference for (+)-ABA, through the plasma membrane, especially in vascular tissues (e.g. phloem companion cells), and is involved in the intercellular ABA signaling pathway (PubMed:20133881, PubMed:20935463, PubMed:24521878, PubMed:26517905). Together with ABCG31, export ABA from the endosperm to deliver it to the embryo via ABCG30 and ABCG40-mediated import to suppress radicle extension and subsequent embryonic growth (PubMed:26334616).[1] [2] [3] [4] [5] Publication Abstract from PubMedAbscisic acid (ABA) is one of the plant hormones that regulate various physiological processes, including stomatal closure, seed germination and development. ABA is synthesized mainly in vascular tissues and transported to distal sites to exert its physiological functions. Many ABA transporters have been identified, however, the molecular mechanism of ABA transport remains elusive. Here we report the cryogenic electron microscopy structure of the Arabidopsis thaliana adenosine triphosphate-binding cassette G subfamily ABA exporter ABCG25 (AtABCG25) in inward-facing apo conformation, ABA-bound pre-translocation conformation and outward-facing occluded conformation. Structural and biochemical analyses reveal that the ABA bound with ABCG25 adopts a similar configuration as that in ABA receptors and that the ABA-specific binding is dictated by residues from transmembrane helices TM1, TM2 and TM5a of each protomer at the transmembrane domain interface. Comparison of different conformational structures reveals conformational changes, especially those of transmembrane helices and residues constituting the substrate translocation pathway during the cross-membrane transport process. Based on the structural data, a 'gate-flipper' translocation model of ABCG25-mediated ABA cross-membrane transport is proposed. Our structural data on AtABCG25 provide new clues to the physiological study of ABA and shed light on its potential applications in plants and agriculture. Cryo-EM structure and molecular mechanism of abscisic acid transporter ABCG25.,Huang X, Zhang X, An N, Zhang M, Ma M, Yang Y, Jing L, Wang Y, Chen Z, Zhang P Nat Plants. 2023 Sep 4. doi: 10.1038/s41477-023-01509-7. PMID:37666961[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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