Figure 4.

Mass spectrometry tryptic map of an hFSH beta subunit expressed in insect cells. One of two possible N-linked glycosylation sites is not used with high fidelity as evidenced by the presence of peptide #17–33, whose molecular ion is equivalent to the peptide hFSHbeta 17–33 mass without glycosylation. From (37) with permission. Tryptic digestion of human FSH produced in insect cells revealed a loss of glycosylation at asparagine 24 demonstrating that this glycosylation site is not consistently glycosylated.