Partial sequencing of the peptides via MS–MS was used to construct the following degenerative primers: GAP 65 DGF (5-ATGATGGTNGAYTGGGGNT TY-3) and GAP 65 DGR (5-AARTANCCIGANGTRAARTG-3), used in a RT-PCR with gastrolith epithelial disk RNA. The entire GAP 65 sequence was obtained through rapid amplification of 5 and 3 cDNA ends (RACE; Clontech SMART RACE; BD Biosciences).