O-Linked glycosylation occurs on basic parotid salivary proline-rich proteins

Interactions between salivary glycoproteins and many oral bacteria have bee n shown to depend on O-linked glycans on salivary glycoproteins. Basic prol ine-rich proteins form the largest group of proteins within human parotid s aliva. In the present study human parotid salivary glycoproteins were separ ated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis or two-di mensional electrophoresis, electroblotted onto nitrocellulose and probed wi th two biotin-labelled lectins from Maclura pomifera (MPA) and Arachis hypo gaea (PNA) which are specific for O-linked (galactose beta 1,3 N-Acetylgala ctosamine) glycans. Lectin binding was detected with avidin-biotin complex and enhanced chemiluminescence. Two-dimensional electrophoresis in combinat ion with lectin binding indicated that only basic parotid salivary glycopro teins bind the lectin MPA. Following removal of terminal sialic acid residu es by sialidase digestion the same glycoproteins were detected by the lecti n PNA. Glycosidase digestion with endo-alpha-N-acetylgalactosaminidase (O-g lycanase) in conjunction with sialidase eliminated MPA binding. Taken toget her these results indicate that many basic parotid salivary glycoproteins c ontain O-glycans, all of which are sialylated.