The nucleotide and deduced amino acid sequence of a rat cysteine string protein.

Cysteine string proteins are novel, heavily lipidated components of synaptic vesicles. They have previously been studied in Drosophila (insect) and Torpedo (fish). To facilitate further investigation of the structure and function of these proteins in mammals, we isolated and sequenced the cDNA and conducted an initial characterization of a rat cysteine string protein. Nucleotide sequencing reveals that this rat protein is highly homologous to the insect and fish cysteine string proteins. At the amino acid level, the fish and rat proteins are 82% identical. The rat cysteine string protein is encoded by an approximately 5 kb mRNA that is ubiquitously expressed in rat brain. Using antibodies that cross-react with the rat protein, we find that the rat cysteine string protein is predominantly associated with nerve endings and synaptic vesicles. Moreover, like its Torpedo (fish) counterpart, it is extensively fatty acylated. It will be of considerable interest to ascertain the functional correlates of these cross-species similarities of cysteine string proteins.