Getting pure populations of taste buds suitable for molecular analysis has hampered the characterization of genes specifically expressed in taste cells. To solve this problem, we prepared specific cDNA libraries from small numbers of taste cells and surrounding epithelium isolated by laser capture microdissection (LCM) and report the discovery of a rhesus monkey novel gene (rmSTG) expressed specifically in taste cells, as found by differential screening of the cDNA libraries and RNA in situ hybridization. RNA in situ hybridization shows the preferential expression of this gene in taste buds from circumvallate, foliate, and fungiform papillae of the tongue. RT-PCR and Northern analysis of RNA from different non-taste organs showed no expression, pointing to a very specialized function of the protein in taste cells. Analysis of extended cDNAs and genomic DNA showed two exons and one intron. Northern analysis of circumvallate papillae showed a transcript of 1.3 kb as established in the gene model. BLAST search analysis showed that the human homolog is localized in the recently completely sequenced HLA class I region of Chromosome 6p21 and is sublocalized to the main susceptibility region for psoriasis vulgaris. The predicted gene encodes a protein of 314 amino acids with an N-terminal signal peptide and cleavage site, suggesting a membrane-bound or secreted protein with an extracellular role in taste cell physiology. The monkey, human, and mouse STG proteins contain potential O-glycosylation sites and tandem repeats inside a region showing -50% similarity with prion proteins.