Piccolo is 1 component of the presynaptic cytomatrix. Bassoon is a large protein which is also found in the presynaptic compartments of rat brain synapses. Bassoon, along with Piccolo, is part of the ensemble of presynaptic proteins that are involved in orchestrating events at the nerve terminal. Bassoon is found in axon terminals of hippocampal neurons where it is highly concentrated in the vicinity of the active zone. Piccolo has a similar distribution and colocalizes with Bassoon in cultured hippocampal cells. Piccolo zinc fingers interact with the dual prenylated rab3A and VAMP2 Synaptobrevin II receptor PRA. Bassoon may be involved in cytomatrix organization at the site of neurotransmitter release. The gene which encodes bassoon maps to human chromosome 3p21.31. The gene which encodes piccolo maps to human chromosome 7q21.11.