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
Affiliations
Franko Mérida-Quesada
Programa de Doctorado en Ciencias mención Modelado de Sistemas Químicos y Biológicos, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
Fernando Vergara-Valladares
Programa de Doctorado en Ciencias mención Modelado de Sistemas Químicos y Biológicos, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
María Eugenia Rubio-Meléndez
Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
Naomí Hernández-Rojas
Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
Angélica González-González
Programa de Doctorado en Ciencias mención Biología Vegetal y Biotecnología, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
Erwan Michard
Instituto de Ciencias Biológicas, Universidad de Talca, Campus Talca, Avenida Lircay, Talca CL-3460000, Chile
Carlos Navarro-Retamal
Instituto de Ciencias Biológicas, Universidad de Talca, Campus Talca, Avenida Lircay, Talca CL-3460000, Chile
Ingo Dreyer
Electrical Signaling in Plants (ESP) Laboratory–Centro de Bioinformática y Simulación Molecular (CBSM), Facultad de Ingeniería, Universidad de Talca, 2 Norte 685, Talca CL-3460000, Chile
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.