Synaptic vesicle structure

The first molecular level model of an organelle is described by Shigeo Takamori, Reinhard Jahn (Max-Planck Institute, Göttingen, Germany), and colleagues. Proteomics, quantitative measurements, and molecular modeling give them a view of an average synaptic vesicle.

The first surprise is that the vesicle is almost smothered in proteins. The group started by identifying 410 proteins associated with purified brain synaptic vesicles, but “if you want to put 400 proteins in the model it exceeds the amount of surface area available,” says Takamori. They suspect that many of the proteins are passengers on only a few vesicles, so instead they measured the copy number of the more abundant proteins. By putting just these 27 proteins in the model, they accounted for almost 70% by mass of the vesicles' protein complement.

Even with these few proteins, “the vesicles are...