Figure 7

Porcine Dsp posttranslational modification sites. A: Diagram showing the three regions (Dsp, Dgp, and Dpp) of porcine Dspp. B: Diagram showing N and O-linked glycosylation sites identified in this study. Among the eight asparagines in the appropriate context for glycosylation, six were determined to be glycosylated (Asn³⁷, Asn⁷⁷, Asn¹³⁶, Asn¹⁵⁵, Asn¹⁶¹, Asn¹⁷⁶). The glycosylation status Asn⁶⁷ was not determined. Asn³¹⁵ was shown to not be glycosylated, possibly due to an O-glycosylation of Thr³¹⁶. In porcine Dsp, it was shown that the N-glycosylations contain, on average, one sialic acid, in the form of N-acetylneuraminic acid, per N-glycosylation. Ser²³⁸ and Ser²⁵⁰ were determined to be GAG attachment sites, with the GAG attachments being comprised of chondroitin 6-sulfate and chondroitin 4-sulfate in a ratio of 7 to 3. O-glycosylations were suggested by blank cycles at Thr²⁰⁰, Thr²¹⁶, and Thr³¹⁶ in samples that were positive for glycosylation by the phenol sulfuric acid assay and eluted early from a size-exclusion column, but no direct evidence for O-glycosylation was obtained and the conclusion that these residues are glycosylated should be considered tentative.