Fig. 3. GAPR-1 is myristoylated in vivo. (A) Positive nanoESI spectrum of the in-gel digest of native GAPR-1. The top panel shows the complete survey spectrum, and the lower panel shows the expanded view from m/z 413 to 417 showing the singly protonated molecular ion of the T1 fragment including the 13C isotope peak. (B) Positive nanoESI product ion spectrum of m/z 414.33. The spectrum shows the key fragments for the myrG structure at m/z 211, 240 and 268 and sequence-specific fragment ions, which identify the peptide as the T1 fragment myrGK of GAPR-1.