Structural Characterization of the Mechanosensitive Channel Candidate MCA2 from Arabidopsis thaliana

Hideki Shigematsu,Kazuko Iida,Kuniaki Nagayama,Hidetoshi Iida,Masataka Nakano,Pratima Chaudhuri,Vladimir N Uversky

doi:10.1371/journal.pone.0087724

Abstract

Mechanosensing in plants is thought to be governed by sensory complexes containing a Ca2+-permeable, mechanosensitive channel. The plasma membrane protein MCA1 and its paralog MCA2 from Arabidopsis thaliana are involved in mechanical stress-induced Ca2+ influx and are thus considered as candidates for such channels or their regulators. Both MCA1 and MCA2 were functionally expressed in Sf9 cells using a baculovirus system in order to elucidate their molecular natures. Because of the abundance of protein in these cells, MCA2 was chosen for purification. Purified MCA2 in a detergent-solubilized state formed a tetramer, which was confirmed by chemical cross-linking. Single-particle analysis of cryo-electron microscope images was performed to depict the overall shape of the purified protein. The three-dimensional structure of MCA2 was reconstructed at a resolution of 26 Å from 5,500 particles and appears to comprise a small transmembrane region and large cytoplasmic region.

Highlights

Plants respond to various environmental stimuli, including light, temperature, wind, and touch, all of which affect growth and development
We previously identified genes that code for potential MS channels or their regulators in Arabidopsis, named MCA1 and its paralog MCA2 [16,17]
MCA2 was shown to be involved in the uptake of Ca2+ in Arabidopsis roots [17]. These findings indicate that MCA1 and MCA2 play important roles in a Ca2+-permeable MS channel system

Summary

Introduction

Plants respond to various environmental stimuli, including light, temperature, wind, and touch, all of which affect growth and development. Wind and touch are examples of mechanical stimuli that generate a Ca2+ signal in the cytoplasm [1]. This signal is thought to be generated through Ca2+-permeable, mechanosensitive (MS) channels in cellular membranes. Bacterial and animal MS channels have so far been studied extensively and characterized in detail at the molecular level [2,3,4]. Homologues of the bacterial MS channel MscS, named MscSlike proteins or MSLs, have recently been identified and characterized in Arabidopsis thaliana [5,10,11,12,13,14,15].

Methods

Results

Conclusion