Topological organization of proteins in an intracellular secretory organelle: The synaptic vesicle Academic Article uri icon


MeSH Major

  • Membrane Proteins
  • Synaptic Vesicles


  • Intact synaptic vesicles prepared from the electric organ of the marine elasmobranch Narcine brasiliensis have eight major polypeptides demonstrable on sodium dodecyl sulfate gels. Six of these copurify with the synaptic vesicles during isolation of vesicles by chromatography on CPG-3000 and, by this criterion, are specific to vesicles. The other two are either shared by many membrane or are contaminants. One of these proteins comigrates with actin. Three different approaches were used to determine which proteins were exposed on the external, cytoplasmic surface of the vesicle and which were internal. The first was susceptibility to the proteases trypsin, Streptomyces griseus protease, and Pronase; the second was labeling by the membrane-impermeable reagent diazotized [125I]iodosulfanilic acid; and the third was iodination catalyzed by lactoperoxidase. In general, the three approaches give the same result: six of the eight proteins are on the external, cytoplasmic surface and two are accessible only after the vesicles are lysed by freezing and thawing or by detergents. Five of the vesicle-specific proteins are external and one is internal. The actin-like protein is internal. Proteins involved in the interaction of vesicles with the presynaptic membrane during exocytosis might be expected to be vesicle specific and external.

publication date

  • January 1979



  • Academic Article



  • eng

PubMed Central ID

  • PMC383991

PubMed ID

  • 291069

Additional Document Info

start page

  • 4126

end page

  • 30


  • 76


  • 8