Mobility of Concanavalin a Receptors in Myelin and Synaptic Membranes

Localization and Characterization of Concanavalin a Receptors in the Synaptic Cleft

“…By comparison, in agreement with data reported by Matus et al (1973) both the inner surface of the synaptic membrane and the PSD bind very little Con A conjugate. Essentially all postsynaptic membranes with a prominent PSD display Con A binding sites which indicates that the presence of Con A receptors may be a property of all asymmetric type synapses (type I) (Gray, 1959;Colonnier, 1968) in rat brain.…”

“…We confirm the observations of Matus et al (1973) and demonstrate that within the cleft a portion of the Con A binding sites are present on the external surface of the postsynaptic membrane overlying the postsynaptic density (PSD). These sites appear to be mainly glycoproteins.…”

“…In the erythrocyte membrane, on the other hand, Triton X-100 removes the majority of the glycoproteins and in doing so removes proteins known to span the membranes (Yu et al, 1973). Second, in nerve membrane areas outside the cleft Matus et al (1973) obtained indications that Con A receptors are mobile. In aldehyde-fixed preparations Con A conjugates distributed diffusely and uniformly over the surface whereas in the absence of prior fixation Con A sites can be induced to reorganize into small clusters.…”

“…The cleft area stains with ruthenium red and periodic acid-Schiff stain (Rambourg and Leblond, 1969;Bondareff, 1967). Recently Matus et al (1973) suggested that concanavalin A (Con A) binding sites may be present in the synaptic cleft. Since Con A binds to mannopyranosyl or glucopyranosyl receptors, the cleft would appear to contain these sugars or closely related molecules.…”

Identification of phosphoglycoproteins obtained from rat brain

“…Nerve endings and synaptosomal plasma membranes have been reported to contain a high concentration of glycoproteins [1,2] and more recently it has been shown that myelin and synaptic membranes contain Concanavalin A receptors [3]. Glycopeptides that possess concanavalin A receptor activities have been recovered from brain tissue by proteolytic treatment of defatted tissue and affinity chromatography utilizing Concanavalin A-Sepharose [4,5] ; mannose rich glycopeptides that bind strongly to Concanavalin A are especially enriched in the myelin-rich fraction and are present in synaptic plasma membranes.…”