Figure 1. Summary of the chimeric subunits studied.

The upper panel shows cartoons of the structures of the chimeric subunits studied. Only the region including the membrane-spanning domains M1, M2 and M3 is shown, as all chimeras were generated by joining subunits within these regions. The residues at the left of M1 belong to the extracellular N-terminal, and the residues at the right of M3 belong to the C-terminal portion (not shown). In the chimeras generated for this work, the β3 subunit contributes the residues at the N-terminal of the joining site, and the ρ1 subunit the residues to the C-terminal. In c7 the joining point is located between residue 272 of β3 and 315 of ρ1, in c1 between β3 253 and ρ1 295, and in c2 between β3 223 and ρ1 265. The lower panel shows an alignment of amino acid residues in this region of the β3 and ρ1 subunits. The membrane-spanning regions are indicated by brackets, and the sites of the joins are indicated by arrows.