Orphan receptors molecular cloning

The answer to this question is not known. However, homology-based molecular cloning techniques have led to the identification of literally hundreds of these receptors each of which conforms to the seven transmembrane domain pattern. The function of many of these receptors and their ligands are unknown such receptors are referred to as orphan receptors. Similarly, there is a considerable diversity of G-proteins. In particular, over 30 different a-subunit types have been described. 

Maenhaut, C. Van Sande, J. Massart, C. et al. The orphan receptor CDNA RDC4 encodes a 5-HTlD serotonin receptor. Biochem. Biophys. Res. Commun. 1991,180, 1460-1468. Ames, R.S. Li, T. Sarau, H.M. et al. Molecular cloning and characterization of the human anaphylatoxin C3a receptor. J. Biol. Chem. 1996, 271, 20231-20234. 

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