Protein piccolo, also termed aczonin, is a neuron-specific presynaptic active zone scaffolding protein that mainly interacts with a detergent-resistant cytoskeletal-like subcellular fraction and is involved in the organization of the interplay between neurotransmitter vesicles, the cytoskeleton, and the plasma membrane at synaptic active zones. It binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics. It also functions as a presynaptic low-affinity Ca2+ sensor and has been implicated in Ca2+ regulation of neurotransmitter release. Piccolo is a multi-domain protein containing two N-terminal FYVE zinc fingers, a polyproline tract, and a PDZ domain and two C-terminal C2 domains. This family corresponds to the second FYVE domain, which resembles a FYVE-related domain that is structurally similar to the canonical FYVE domains but lacks the three signature sequences: an N-terminal WxxD motif (x for any residue), the central basic R(R/K)HHCRxCG patch, and a C-terminal RVC motif.
Jiyao W et al.(2023). "The conserved domain database in 2023.",