A copper cofactor for the ethylene receptor ETR1 from Arabidopsis

The ETR1 receptor from Arabidopsis binds the gaseous hormone ethylene, A co pper ion associated with the ethylene-binding domain is required for high-a ffinity ethylene-binding activity. A missense mutation in the domain that r enders the plant insensitive to ethylene eliminates both ethylene binding a nd the interaction of topper with the receptor. A sequence from the genome of the cyanobacterium Synechocystis sp, strain 6803 that shows homology to the ethylene-binding domain of ETR1 encodes a functional ethylene-binding p rotein. On the basis of sequence conservation between the Arabidopsis and t he cyanobacterial ethylene-binding domains and on in vitro mutagenesis of E TR1, a structural model for this copper-based ethylene sensor domain is pre sented.