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Fig. 6 Distinct subunit compositions of AChRs in slow and fast muscles underlie the fiber-type specific phenotypes in the love sofa mutant. Wild-type (A) and love sofa (B) larvae were doubly labeled with an antibody for ε/γsubunits (green) and α-BTX (magenta). Optical sections corresponding to slow muscle fibers and fast muscle fibers are shown. Scale bar, 20 μm. C, A schematic depicting the hypothesis. In wild-type larvae (top), pentamers of slow muscles comprise αβδ, whereas those in fast muscle comprise αβδε/γ. Red triangle represents the ligand (ACh or α-BTX). In the love sofa mutant (bottom), the δ subunit harbors a L332P mutation (shown with an asterisk and yellow). As a result, the binding of ligand to the pockets between α and δ is inhibited in fast muscles.