Figure 1.

Identification of the RDTASIA variant of γ₂ subunit isolated from bovine brain heterotrimer. (A) Matrix-assisted laser desorption ionization–MS of an HPLC fraction containing γ variant (m/z 7,594), unmethylated γ₂ (m/z 7,738), γ₅ C-terminal variant (m/z 7,502; ref. 35), and γ₃ (m/z 8,284). (B) Edman sequencing analysis of an HPLC fraction containing truncated/modified γ isoforms for the first four cycles. The sequenced fraction contained two independent sequences, γ₃ (minor) and RDTASIA γ₂ (major). (C) Electrospray ionization tandem MS analysis of RDTASIA variant of γ₂. A tandem MS spectrum of RDTASIA γ₂ isoform is shown. [M + 8H]⁸⁺ ion, m/z 950.3 selected, average of 18 scans. (Inset) Table of predicted and observed ions.