The Calcium Binding Sites of Synaptic Vesicles of the Frog Sartorius Neuromuscular Junction

Secretory functions of egg cortical granules in fertilization and development: A critical review

“…However, identification of specific granule types or intraorganelle sites of calcium binding was not possible with their rudimentary fractionation procedure. The localization of calcium in the plasma membrane and cortical (secretory) granule membranes in unfertilized sea urchin eggs is consistent with the localization at similar sites in mammalian sperm [Chandler and Battersley, 19761 and various somatic secretory cells [Clemente and Meldolesi, 1975;Cramer et al, 1976;Herman et al, 1973;Oschman et al, 3 24 Schuel 1974;Politoff et al, 1974;Sat0 et al, 19751 . Such focal deposits may represent calciumbinding sites, which suppress membrane fusion necessary to initiate exocytosis.…”

Calcium transport in a vesicular membrane preparation from rat brain synaptosomes

“…thesis) that acetylcholine formed in intact synaptosomes from labeled choline is recovered within the same fraction. In addition, synaptic vesicles at the frog neuromuscular junction were shown to posses calcium-binding sites [18]. The alternative possibility that the calcium-transporting synaptosomal vesicles originate from endoplasmic reticulum type membrane is, of course, not ruled out since the enzyme marker glucose-6-phosphatase for brain endoplasmic reticulum [19] is present in every synaptosomal vesicles preparation tested.…”

ATP-Dependent calcium uptake by cholinergic synaptic vesicles isolated fromtorpedo electric organ

“…The structural localization of the nonmitochondrial Ca § sequestration mechanism is still a matter of discussion. -Synaptic vesicles may be formed from the intraterminal smooth reticulum [12,15], which is known to accumulate calcium [17].When fixed in the presence of calcium, synaptic vesicles exhibited a dense granule, generally considered to be a calcium precipitate [6,14,33,42]. Finally, a Ca ++ dependent ATPase is present in a purified fraction of synaptic vesicles [7].…”