Identification and localization of low-molecular-mass GTP-binding proteins associated with synaptic vesicles and other membranes.
GTP-binding proteins were studied in synaptic vesicles prepared from bovine brain by differential centrifugation and separated further from plasma membranes using gel permeation chromatography. Following separation by SDS-PAGE of proteins from the different fractions, and transfer to nitrocellulose sheets, the presence and localization of low-molecular-mass GTP-binding proteins were assessed by [alpha-32 P]GTP binding. The vesicle-membrane fraction (SV) was enriched in synaptophysin (p38, a synaptic vesicle marker) and contained low-molecular-mass GTP-binding proteins; these consisted of a major 27 kDa protein and minor components (Mr 26 and 24 kDa) which were trypsin-sensitive and immunologically distinguishable from ras p21 protein. GTP-binding proteins of low molecular mass, but displaying less sensitivity to trypsin, were also found in the plasma membrane fraction (PM; enriched in Na+/K(+)-ATPase). In addition, the PM fraction contained GTP-binding proteins with higher Mr (Gi alpha and G0 alpha), together with another GTP-binding protein, ras p21. Putative function(s) of these GTP-binding proteins with low mass are discussed.
Matsuoka
I
I
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London, U.K.
Dolly
J O
JO
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D002458:Cell Fractionation; D002462:Cell Membrane / Q000032:analysis*; D002850:Chromatography, Gel; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D015151:Immunoblotting; D008970:Molecular Weight; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013572:Synaptic Vesicles / Q000032:analysis*
D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000254:Sodium-Potassium-Exchanging ATPase