Molecular mechanisms of signal reception and transduction in taste and smell are being studied; particular emphasis is placed on studies of G- protein mediated signaling. Mutagenesis studies of the G-protein alpha- subunit which appears to function in bitter taste reception have revealed detailed structure-function information relevant to the mechanism of G- protein activation. A taste-tissue cDNA library has been constructed and molecular cloning studies indicate that a G-protein gamma-subunit, that closely resembles the major gamma-subunit of photoreceptor cones, is expressed in the circumvallate papilla. Immunolocalization of the novel G- protein gamma-subunit, gamma8, that is found in developing olfactory and vomeronasal neurons has continued. The importance of C-terminal isoprenylation of G-protein gamma-subunits has been investigated through functional characterization of differentially modified beta gamma- heterodimers.