Figure 1.

Alignment of amino acid residues belonging to the extracellular ligand-binding domains for C. elegans LGC-53, human/rat ρ1, and human/rat β3. Numbering corresponds to the mature protein sequence. Residues that are identical or functionally similar are emphasized in black or gray, respectively. Loops are critical homologous motifs that bind ligands for the entire Cys-loop superfamily, characterized by a Cys-13-Cys sequence. Binding occurs at interface sites between the principal (+) and complimentary (−) sides of adjacent subunits.