Deglycosylation of glycoproteins by trifluoromethanesulfonic acid

Amino acid sequence homologies and glycosylation differences between the fourth component of murine complement and sex-limited protein

Limited primary sequence data have been obtained for all three subunits of the fourth component of murine complement (C4) and its related homologue, the sex-limited protein (Slp). These data show a high degree of NH2-terminal homology between C4 and Slp: four of the six residues identified for the alpha chain, seven of eight for the beta chain, and four of four for the gamma chain. This suggests that apparent molecular weight differences between C4 and Slp subunits are not, as previously suggested, due to a shift in the proteolytic processing sites in the pro-Slp polypeptide molecule. Chemical deglycosylation (apparently complete) of the C4 and Slp alpha chains with trifluoromethanesulfonic acid removes the molecular weight difference between them, suggesting that acquisition of extra glycosylation sites in the latter is responsible for this difference.

Tissue- and developmental stage-specific forms of a neural cell surface antigen linked to differences in glycosylation of a common polypeptide

We have previously identified a cell surface glycoprotein of the mouse nervous system named brain cell surface protein-2 (BSP-2). Here we report that this antigen is not a single, discrete entity, but a family of antigenically and structurally related molecules. Three components of 180, 140, and 120 K were characteristic for more mature nervous tissues. Adult cerebral cortex contained the 140-K and 120-K antigens, adult spinal cord only the 120-K, and dorsal root ganglia from young mice mainly the 180-K component. Very different forms of the antigen that migrated as a diffuse zone from 180-250-K in SDS-polyacrylamide gels were found in immature nervous tissues. A molecule different from the previous ones was found in a neuroblastoma line. Evidence is presented that the structural diversity of BSP-2 is due to differences in glycosylation. This result indicates that cell type- and developmental stage-specific glycoprotein patterns previously found in the nervous system may in part be due to different glycosylation of identical polypeptides. The finding that a neural cell surface protein may be glycosylated in different ways has important implications for the generation of cell surface specificity.