Functional topography of the myelin-associated glycoprotein. I. Mapping of domains by electron microscopy.
The functional topography of the myelin-associated glycoprotein (MAG) was investigated by electron microscopic analysis of rotary-shadowed molecules of a MAG fragment (MAG 90) comprising the five immunoglobulin-like domains of the extracellular part of the molecule. MAG 90 molecules appeared as rod-like structures (18.5 +/- 1.2 nm long and 4.0 +/- 0.8 nm wide) with a globular domain at one end. Antibodies directed against the amino- and carboxy-terminus of MAG 90 interacted with the non-globular terminal region, indicating that the molecule is bent in the globular region with the amino- and carboxy-terminal arms in close apposition to each other. An antibody which interferes with the binding of MAG to neurons interacted predominantly with the globular domain of MAG 90. The fibril-forming collagen types I, III and V bound mainly to the non-globular terminal region of MAG 90, whereas the majority of heparin molecules interacted with the globular region of the molecule. The L2/HNK-1 carbohydrate structure was localized at the non-globular region in the protein fragment comprising the fourth and fifth immunoglobulin-like domains.
Fahrig
T
T
Department of Neurobiology, Swiss Federal Institute of Technology, Zürich.
Probstmeier
R
R
Spiess
E
E
Meyer-Franke
A
A
Kirchhoff
F
F
Drescher
B
B
Schachner
M
M
D000818:Animals; D000906:Antibodies / Q000276:immunology; D001666:Binding Sites, Antibody; D003094:Collagen / Q000378:metabolism; D006493:Heparin / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D009185:Myelin Proteins / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure*; D018992:Myelin-Associated Glycoprotein; D016626:Shadowing Technique, Histology
D000906:Antibodies; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D006493:Heparin; D003094:Collagen