● G protein linked receptors (GPLRs, GPCRs, 7TM) comprise the most numerous family of metabotropic signaling receptors, so the GPCRs are the largest protein family known.
Protein kinases are often anchored to a scaffold protein that either holds the kinase in a latent state close to its activating receptor, or facilitates the flow of information from one kinase to the next kinase in a signaling cascade.
● Histidine-kinase-associated receptors activate two-component signaling pathways in which the receptor receives a signal and transmits it, via phosphorelay, to a partner response regulator protein. In the phosphorelay, the histidine kinase acts as an autokinase by phosphorylating its own histidine residue before immediately transfering the phosphate to a second intracellular signaling protein in the receiver domain.
● Receptor tyrosine kinases phosphorylate specific tyrosines on intracellular signaling proteins.
● Protein tyrosine-kinase-associated receptors associate with specific intracellular proteins that possess tyrosine kinase activity.
● Receptor-like tyrosine phosphatases remove the phosphate groups from tyrosine residues of specific intracellular signaling proteins.
● Receptor serine/threonine kinases phosphorylate specific serine or threonine residues on associated latent gene regulatory proteins.