Fig. 2.

Time course of chymotryptic digestion to obtain increased sequence coverage of the fourth transmembrane domain of the GABA_A receptor α₁ subunit using LC-MS. A, Diagram of a GABA_A receptor subunit composed of four transmembrane spanning regions with extracellular N- and C termini and the assembly of five such subunits to form a pentameric chloride channel. B, Overlapping peptides of the entire fourth TMD of the α₁ subunit of the GABA_A receptor from the sequential digestion with Lys-C and chymotrypsin for varying lengths of time. C, Peptide intensities from MS1 spectra of the indicated TMD4 peptides that were produced during the chymotryptic digestion time course.