Purification of a presynaptic membrane protein that mediates a calcium-dependent translocation of acetylcholine.
A protein, which we call "mediatophore," that mediates calcium-dependent release of acetylcholine from proteoliposomes has been purified from the presynaptic plasma membrane. About 250 micrograms of this material was obtained from 500 g of Torpedo marmorata electric organ. Precipitation of the protein and subsequent removal of associated lipids inactivated the protein, which then became water soluble; this permitted evaluation of its Stokes radius (52 A) and its sedimentation coefficient (9.8 +/- 0.75 S) and, hence, an approximate molecular mass of 210 +/- 16 kDa could be determined. PAGE analysis showed that the protein is made of 17-kDa subunits, not linked by disulfide bonds. When this material was observed by electron microscopy after negative staining, the apparently pentameric structures had an average diameter of about 7 nm.
Israël
M
M
Morel
N
N
Lesbats
B
B
Birman
S
S
Manaranche
R
R
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002352:Carrier Proteins / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000302:isolation & purification*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000302:isolation & purification*; D009469:Neuromuscular Junction / Q000032:analysis*; D014101:Torpedo
D002352:Carrier Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C050299:mediatophore; D000109:Acetylcholine; D002118:Calcium