Electron microscopic evidence for a mucin-like region in chick muscle alpha-dystroglycan.
alpha-Dystroglycan has been isolated from chicken cardiac muscle and its molecular weight was estimated to be approximately 135 kDa. The avian protein interacts with murine Engelbreth-Holm-Swarm (EHS) tumor laminin via interaction with the C-terminal LG4 and LG5 domains (fragment E3) of the laminin alpha-chain. This laminin binding is calcium-dependent and can be competed by heparin. Electron microscopy investigation on the shape of alpha-dystroglycan suggests that the core protein consists of two roughly globular domains connected by a segment which most likely corresponds to a mucin-like central region also predicted by sequence analysis on mammalian isoforms. This segment may act as a spacer in the dystrophin-associated glycoproteins complex exposing the N-terminal domain of alpha-dystroglycan to laminin in the extracellular space.
Brancaccio
A
A
Department of Biophysical Chemistry, Biozentrum, University of Basel, Switzerland.
Schulthess
T
T
Gesemann
M
M
Engel
J
J
D000818:Animals; D002645:Chickens; D003598:Cytoskeletal Proteins / Q000302:isolation & purification / Q000648:ultrastructure*; D049030:Dystroglycans; D007797:Laminin / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000302:isolation & purification / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009077:Mucins / Q000648:ultrastructure; D009206:Myocardium / Q000737:chemistry*; D011485:Protein Binding
D003598:Cytoskeletal Proteins; D007797:Laminin; D008562:Membrane Glycoproteins; D009077:Mucins; D049030:Dystroglycans