What are the similarities between G protein coupled receptors and receptor tyrosine kinases?

They are both transmembrane proteins and cell surface receptors. Additionally, they are both involved in cell signaling pathways, such as cAMP for G-Protein Coupled Receptors (GPCRs) and the MAP kinase cascade for Receptor Tyrosine Kinases (RTKs). Another similarity is that both are inactive until they bind to a ligand on a receptor protein. GPCRs are normally activated by neurotransmitters or hormones, while RTKS are normally activated by growth factors which bind to their extracellular domains. Both also lead to conformational changes in the receptors. For the majority of RTKS, the conformational changes promote trans-autophosphorylation of each tyrosine kinase domain and release of cis-autoinhibtion. Upon the binding of ligands to GPCRs (on the extracellular side of the helix bundle), a conformational change occurs and the G proteins are activated. This occurs via the transfer of GDP/GTP correlated with the Ga subunit.