Ethylene receptor related to bacterial two-component regulators. Acts as a redundant negative regulator of ethylene signaling. Binds 1 copper ion per dimer. Heteromer with ETR1 (PubMed:18577522). Binds to MRF3/ECIP1 (PubMed:21631530). Expressed in embryos, etiolated seedlings, leaves, roots, inflorescences, stamens, pollen cells and tapetum cells. Moderate expression in carpels. Not induced by ethylene. Autophosphorylated predominantly on Ser residues. Belongs to the ethylene receptor family. The article by Li et al was retracted by the editors after publication. Concerns were raised regarding a number of figure panels, such as partial overlap between the panels and duplication of protein gel analysis.