Cysteine-string proteins as templates for membrane fusion: models of synaptic vesicle exocytosis

Cysteine-string proteins are relatively small, cysteine-rich components of synaptic vesicle membranes. Recent investigations demonstrated that at least 11 of the 13 cysteine residues of the Torpedo cysteine-string protein are fatty acylated. This exceptional level of fatty acylation occurs along a short stretch (less than 25 residues) of amino acids which are flanked on either side by very polar amino and carboxy termini. This amphipathic structure may have unique capabilities to catalyze events at membrane interfaces. We propose two distinct pathways to explain how these capabilities might subserve membrane fusion and exocytosis.