Voltage-gating and cytosolic Ca2+ activation mechanisms of Arabidopsis two-pore channel AtTPC1

• Published in: Proceedings of the National Academy of Sciences - PNAS 2021-12, Vol.118 (49), p.1-10
• Main Authors: Ye, Fan, Xu, Lingyi, Li, Xiaoxiao, Zeng, Weizhong, Gan, Ninghai, Zhao, Cheng, Yang, Wei, Jiang, Youxing, Guo, Jiangtao
• Format: Article
• Language: English
• Subjects: Biological Sciences; Calcium; Calcium channels (voltage-gated); Calcium ions; Channel gating; Conformation; Depolarization; Domains; EF-hand; Ion channels; Ions; Membrane potential; Membranes
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2113946118

Arabidopsis thaliana two-pore channel AtTPC1 is a voltage-gated, Ca2+-modulated, nonselective cation channel that is localized in the vacuolar membrane and responsible for generating slow vacuolar (SV) current. Under depolarizing membrane potential, cytosolic Ca2+ activates AtTPC1 by binding at the EF-hand domain, whereas luminal Ca2+ inhibits the channel by stabilizing the voltage-sensing domain II (VSDII) in the resting state. Here, we present 2.8 to 3.3 Å cryoelectron microscopy (cryo-EM) structures of AtTPC1 in two conformations, one in closed conformation with unbound EF-hand domain and resting VSDII and the other in a partially open conformation with Ca2+-bound EF-hand domain and activated VSDII. Structural comparison between the two different conformations allows us to elucidate the structural mechanisms of voltage gating, cytosolic Ca2+ activation, and their coupling in AtTPC1. This study also provides structural insight into the general voltage-gating mechanism among voltage-gated ion channels.