Structure and function of G protein coupled receptors.

The G protein coupled receptors (GPC-Rs) comprise a large superfamily of genes encoding numerous receptors which all show common structural features, e.g., seven putative membrane spanning domains. Their biological functions are extremely diverse, ranging from vision and olfaction to neuronal and endocrine signaling. The GPC-Rs couple via multiple G proteins to a growing number of recognized second messenger pathway, e.g., cAMP and phosphatidyl inositol turnover. This review summarizes our current knowledge of the molecular mechanisms by which the GPC-Rs activate second messenger systems, and it addresses their regulation and structure.