Figure 7.

AziISO photolabeled residues within the β₃-subunits of α₁β₃ and α₁β₃γ_2L GABA_A receptors. Mass spectra of β₃-subunit AziISO photolabeled residues β₃-M3′ V290 (A) and β₃-M2′ I255/β₃-M2′ I264 (B) within α₁β₃ and α₁β₃γ_2L GABA_A receptors, respectively. Focused view the spectrum within ∼350–825 (A) and 280–590 m/z (B), with b (red), y (blue), and precursor ions (green) shown. Predicted photolabeled residues is shown in bold, underlined, and is indicated by a green asterisk. Above the spectra are the subunit peptide sequences that contain the β₃-subunit transmembrane helices. Predicted photolabeled residue is shown in bold, underlined, and is indicated by a green asterisk. See the Supplemental Material for associated peptide fragment tables.