Ethylene receptor related to bacterial two-component regulators. Acts as a redundant negative regulator of ethylene signaling (PubMed:15466228, PubMed:15703053). In the presence of ethylene, the auto-kinase activity of ETR1 is inhibited and the non-phosphorylated kinase domain binds tightly to the corresponding domain of EIN2 (PubMed:20591837). ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Binds 1 copper ion per dimer. Homodimer; disulfide-linked. Heteromer with ERS1, ERS2, ETR2 and EIN4. Interacts with AHP1, AHP2 and AHP3. Interacts with RTE1 (PubMed:10930573, PubMed:18577522, PubMed:20952388, PubMed:7759498). Interacts with EIN2 (PubMed:19769567). Leaves, roots, stems, seedlings, flowers, anthers, carpels and ovules. The GAF domain is sufficient to mediate heteromerization. Autophosphorylated. Phosphorylation at His-353 modulates the interaction with EIN2. No visible phenotype in ethylene response; due to redundancy with ERS1. Ers1 and etr1 double mutants display a constitutive ethylene-response phenotype. Belongs to the ethylene receptor family.