Plants (Dec 2022)

TPC1-Type Channels in <i>Physcomitrium patens</i>: Interaction between EF-Hands and Ca<sup>2+</sup>

  • Franko Mérida-Quesada,
  • Fernando Vergara-Valladares,
  • María Eugenia Rubio-Meléndez,
  • Naomí Hernández-Rojas,
  • Angélica González-González,
  • Erwan Michard,
  • Carlos Navarro-Retamal,
  • Ingo Dreyer

DOI
https://doi.org/10.3390/plants11243527
Journal volume & issue
Vol. 11, no. 24
p. 3527

Abstract

Read online

Two-pore channels (TPCs) are members of the superfamily of ligand-gated and voltage-sensitive ion channels in the membranes of intracellular organelles of eukaryotic cells. The evolution of ordinary plant TPC1 essentially followed a very conservative pattern, with no changes in the characteristic structural footprints of these channels, such as the cytosolic and luminal regions involved in Ca2+ sensing. In contrast, the genomes of mosses and liverworts encode also TPC1-like channels with larger variations at these sites (TPC1b channels). In the genome of the model plant Physcomitrium patens we identified nine non-redundant sequences belonging to the TPC1 channel family, two ordinary TPC1-type, and seven TPC1b-type channels. The latter show variations in critical amino acids in their EF-hands essential for Ca2+ sensing. To investigate the impact of these differences between TPC1 and TPC1b channels, we generated structural models of the EF-hands of PpTPC1 and PpTPC1b channels. These models were used in molecular dynamics simulations to determine the frequency with which calcium ions were present in a coordination site and also to estimate the average distance of the ions from the center of this site. Our analyses indicate that the EF-hand domains of PpTPC1b-type channels have a lower capacity to coordinate calcium ions compared with those of common TPC1-like channels.

Keywords