Membrane association of presynaptic cytomatrix protein bassoon

Components of the specialized cytomatrix at active zones of presynaptic ner ve terminals are thought to be involved in organizing synaptic events such as immobilisation or translocation of synaptic vesicles and assembling acti ve zone components. The 420-kDa non-transmembrane protein Bassoon is a spec ific component of the presynaptic cytomatrix that shares features with both cytoskeleton-associated and peripheral-membrane proteins. Using immunogold electron microscopy we show here that synapse associated Bassoon is distri buted in a subregion of active zones. Using a biochemical assay we show tha t a fraction of Bassoon is membrane associated. Electron microscopy perform ed on the same biochemical fraction further revealed that Bassoon is associ ated with vesicular structures. Together these data suggest that at least a fraction of Bassoon is associated with a membraneous compartment in neuron s. (C) 2000 Academic Press.