Enhancement of synaptic vesicle attachment to the plasma membrane fraction by copper

Synaptic vesicles from rat brain were labeled with¹²⁵I, and the association of the vesicles with other subcellular components of brain was examined using a centrifugation assay. Copper at micromolar concentrations enhances the binding of the vesicles to the synaptic membrane as well as other fractions. Magnesium, Ca²⁺, and calmodulin with Ca²⁺ are ineffective. There is virtually no binding of synaptic vesicles to the microtuble fraction and only a slight enhancement with Cu²⁺. These findings support the hypothesis that Cu may serve as a bridge between synaptic vesicles and the plasma membrane.