Figure 4. Functional analysis of the ORCO N-terminus.

(a-c) Left: Representative whole cell current traces to the indicated stimuli with two-electrode voltage-clamp in Xenopus oocytes injected with cRNAs for the indicated combinations of wildtype or mutant D. melanogaster ORs. ORCO^6Mut contains amino acid substitutions in the six top-ranked N-terminal residues (A23S, M24A, F30A, M31A, H32A, N33A); ORCO^Δ23-33 bears a deletion of this region (A23-N33). Ligand solutions were applied for 3 s (arrowheads). Right: Quantification of current amplitudes (mean ± SEM; n = 5 oocytes for wildtype ORCO and ORCO^6Mut; n = 4 for ORCO^Δ23-33).