NMR Detection and Structural Modeling of the Ethylene Receptor LeETR2 from Tomato

The gaseous plant hormone ethylene influences many physiological processes in plant growth and development. Plant ethylene responses are mediated by a family of ethylene receptors, in which the N-terminal transmembrane domains are responsible for ethylene binding and membrane localization. Until now, little structural information was available on the molecular mechanism of ethylene responses by the transmembrane binding domain of ethylene receptors. Here, we screened different constructs, fusion tags, detergents, and purification methods of the transmembrane sensor domain of ethylene receptors. However, due to their highly hydrophobic transmembrane domain (TMD), only a KSI-fused LeETR2(1–131) from tomato yielded a good-quality nuclear magnetic resonance (NMR) spectrum in the organic solvent. Interestingly, a dimer model of LeETR2(1–131) built by the AlphaFold2 algorithm showed greatly converged structures. The interaction analysis of ethylene and LeETR2(1–131) using molecular docking and molecular dynamics (MD) simulations demonstrated the potential binding sites of ethylene in LeETR2(1–131). Our exploration provides valuable knowledge for further understanding of the ethylene-perception process in ethylene receptors.