Biochemical characterization of polypeptide components involved in neurite fasciculation and elongation.

Polypeptide components and carbohydrate linkage types of F11 antigen and G4 antigen, two chick cell-surface glycoproteins implicated in neurite fasciculation and elongation [Rathjen, F.G., Wolff, J.M., Bonhoeffer, F. and Rutishauser, U. (1987) J. Cell Biol. 104, 343-353], have been studied in comparison to mouse L1 antigen. Tryptic fingerprint analysis does not reveal any relation of the 130-kDa components of G4 or F11 antigens to each other or to neural cell-adhesion molecules. The 180/190-kDa component of G4 antigen comprises parts of the 130-kDa and 80/65-kDa components and shares a sequence corresponding to the amino terminus of the G4 130-kDa component as shown serologically with anti-peptide sera. This closely parallels the relationship found for mouse L1 antigen components. In contrast, the F11 170-kDa component is different from the F11 130-kDa component, as shown serologically and by fingerprint analysis. A combination of chemical and enzymatic deglycosylation methods reveals that while O-glycosylation cannot be detected F11 130-kDa, G4 130-kDa and L1 140-kDa components contain N-linked carbohydrates. Endoglycosidase H treatment shows that the oligosaccharides present in the G4 130-kDa component and mouse L1 are mostly of the complex type, while the F11 130-kDa component consists of two populations, one containing mainly complex-type carbohydrates and a second containing high-mannose/hybrid-type carbohydrates.