Piccolo, also referred to as Aczonin, is a large protein which consists of an N-terminal Zn2+ finger, several piccolo-bassoon homology domains and C-terminal PDZ and C2 domains. In general it is found together with bassoon, a related huge multi-domain protein of the CAZ (cytoskeletal matric assembled at active zones). Piccolo is a scaffolding protein for proteins involved in endo- and exocytosis of synaptic vesicles. Piccolo has also been shown to interfere with clathrin medicated endocytosis by binding to the F-actin and dynamin binding protein Abp1.