In a new study, American researchers have discovered the role of the third intracellular loop of GPCR in the GPCR signal transduction mechanism, indicating the possibility of adopting more targeted drug discovery methods and developing new drugs.   More than one-third of the drugs approved by the United States Food and Drug Administration (FDA) function by targeting G protein-coupled receptors (GPCRs). The human body has over 800 types of GPCRs,…