Characterization of the sequence and expression of a Ykt6 prenylated SNARE from rat

The Ykt6 protein represents a novel soluble N-ethylmaleimide-sensitive fusion protein receptor (SNARE), as it is the only one known without a hydrophobic transmembrane region at the carboxy terminus. For this SNARE, however, membrane interaction is thought to be mediated through a cysteine/aliphatic/aliphatic/methionine or histidine (CAAX) C-terminal motif, a consensus sequence involved in prenylated membrane anchoring. To date, two full-length Ykt6 cDNAs have been reported, these being in yeast and human, with a further protein predicted from a Caenorhabditis elegans cosmid. Using a mouse EST clone identified as having 65% homology with the human Ykt6, we isolated a cDNA clone encoding the rat Ykt6 homolog (rYkt6). Sequence analysis of rYkt6 demonstrated that a high level of species conservation exists between the rat and human prenylated SNAREs, as both the nucleotide and amino acid sequences share >90% homology. Mammalian Ykt6 is shown here for the first time to be constitutively expressed in a variety of tissues. The species conservation and ubiquitous expression of prenylated SNAREs hence may be indicative of an important and central role for these proteins in cellular protein trafficking.