Synaptotagmin IV (SYT4)

Although retaining the characteristic 5-domain structure of the other synaptotagmins, Syt4 is considerably more divergent at the level of amino acid sequence. In the most highly conserved C2 domain, Syt1 and Syt2 share 88% sequence identity, whereas Syt4 has only approximately 45% identity to either. Syt4 is expressed in many regions of the nervous system but is undetectable in extraneural tissues. The 3 murine synaptotagmins have differential expression patterns in the brain.The 425-amino acid protein is approximately 90% identical to the rodent sequences. Sequence analysis predicted that, like the rat protein, human SYT4 contains a serine residue replacing aspartate in the C2A domain, which disables calcium or phospholipid binding in the rat protein.