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. Expressed in etiolated seedlings, leaves, roots and stems. Highly expressed in flowers, stamens, pollen cells, tapetum cells, carpels and ovules. By ethylene. Autophosphorylated predominantly on Ser residues. Belongs to the ethylene receptor family.