Synaphin: a protein associated with the docking/fusion complex in presynaptic terminals.

We previously identified a 19 kDa protein associated with the docking/fusion complex involved in neurotransmitter release. A cDNA for this protein was cloned from a bovine brain cDNA library using an oligonucleotide probe based on its partial amino acid sequence. The protein (named synaphin) encoded by the cDNA is a very hydrophilic protein rich in glutamic acid and lysine residues. It lacks any putative transmembrane segments or strongly hydrophobic domains. Immunoblots with antibodies against synaphin detected the protein only in the nervous system among the tissues examined. In brain, it exists mainly in the soluble fraction and is scarce in synaptic vesicles.