May act early in the ethylene signal transduction pathway, possibly as an ethylene receptor, or as a regulator of the pathway. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Binds 1 copper ion per dimer. Homodimer; disulfide-linked. Higher expression in arils than in seeds. Constitutive expression during ripening. Activation probably requires a transfer of a phosphate group between a His in the transmitter domain and an Asp of the receiver domain. Belongs to the ethylene receptor family.