Figure 4.

Localization of residues important for PS inhibition within M1. (a) Subdivision of the M1 domain, including the M1–M2 linker, into three segments, designated X, Y, and Z. Asterisks indicate conserved residues at positions 259 and 261, arrows represent boundaries of the X segment (residues 255–264), Y segment (residues 265–273), and Z segment (residues 274–282). (b) PS sensitivity of chimeric receptors in which UNC-49C sequences corresponding to the X, Y, and Z segments have been swapped into the QF-R subunit in different combinations. Bars at the left represent the M1 plus M1–M2 linker region in (a). Closed portions are UNC-49C, open are UNC-49B. Black dots represent UNC-49B to UNC-49C mutations at positions 259, 261, and 305. PS IC₅₀ values were determined by generating PS dose–response curves at EC₅₀ GABA (n⩾3 ooctyes for each molecule; Table 2).