TPC1-Type Channels in Physcomitrium patens: Interaction between EF-Hands and Ca²

Area of Science:

• Molecular Biology
• Plant Physiology
• Biophysics

Background:

• Two-pore channels (TPCs) are crucial ion channels in eukaryotic intracellular organelles.
• Plant TPC1 channels typically exhibit conserved structures for calcium (Ca2+) sensing.
• Mosses and liverworts possess TPC1-like channels (TPC1b) with divergent Ca2+ sensing domains.

Purpose of the Study:

• To investigate the structural and functional differences between TPC1 and TPC1b channels in the model plant *Physcomitrium patens*.
• To analyze the impact of variations in EF-hand domains on calcium ion binding in TPC1b channels.

Main Methods:

• Identification and characterization of TPC1 channel family members in *Physcomitrium patens*.
• Generation of structural models for the EF-hand domains of PpTPC1 and PpTPC1b channels.
• Molecular dynamics simulations to assess calcium ion coordination and binding affinity.

Main Results:

• *Physcomitrium patens* genome encodes two ordinary TPC1 and seven TPC1b channel types.
• TPC1b channels exhibit critical amino acid variations in their EF-hands.
• Structural modeling and simulations revealed a lower capacity for calcium ion coordination in PpTPC1b EF-hands compared to PpTPC1.

Conclusions:

• TPC1b channels in *Physcomitrium patens* possess altered calcium-binding properties due to EF-hand domain variations.
• These findings highlight evolutionary divergence in plant TPC channel function.
• The study provides insights into the molecular mechanisms underlying calcium ion transport regulation in plants.