Figure 3.

Protein sequence comparison between the putative ethylene receptors. (A) Amino acid sequence alignment of ETR2 and ETR1. Similar amino acids are shaded. The five motifs found in ETR1 corresponding to those of the bacterial histidine kinases (H, N, G1, F, G2) are underlined. Three residues corresponding to the residues conserved in the bacterial receiver modules are indicated by ∗. (B) Amino acid sequence alignment of the amino-terminal domains of Arabidopsis ETR2, ETR1, and ERS and tomato NR. Putative transmembrane segments are underlined. Amino acids that are mutated in ethylene-insensitive mutants are boxed.