Figure 5

Peptides derived from purified CnPC deglycosylated with PNGaseF in¹⁸O-labeled water. The complete sequence was predicted from cDNA amplified by Leebs et al. and confirmed in our lab. Fully identified peptides are indicated in blue; peptides with matching sequences but incorrect masses are indicated in grey. Three (Asn139, Asn202, and Asn289) of the potential N-linked glycosylated sites showed a 3-dalton increase in mass, consistent with deamidation of the asparagine residue and incorporation of an ¹⁸O atom. The fourth potential N-linked glycosylated site (Asn350) was not captured on mass spectrometry on multiple attempts. Therefore, the glycosylation status of this site remains unknown. Natural deamidation (i.e. 1-dalton increase in mass at sites with asparagine that is not part of the N-X-S/T sequon or glutamine) was rare.