Question

What is a tyrosine kinase receptor (RTK)? Describe how this type of receptor works. Once activated, what kind of enzyme is needed to deactivate the receptor? Explain

Answer 1

A tyrosine kinase receptor is a specialized type of receptor that is associated to an enzyme. These receptor are located in the surface of the cell membrane and their intracellular domain is composed in fact, by an enzyme. This enzyme is called kinase and it is able to transfer a phosphate group to a protein or a molecular messenger. The phosphate group is specifically transferred to a tyrosine domain in a protein, for this reason the name “tyrosine kinase”.

In order to initiate the signaling cascade, some tyrosine kinase receptor must dimerize in order to be activated. In normal circunstances, the extracellular ligand of the receptor will bind to two tyrosine kinase receptors. Once this happens, both receptors will dimerize. This will lead to the contact of the intracellular domains of both receptors, phosphorylating the tyrosine domain (autophosphorylation) and transmitting the signal. Once, the receptor was activated, a group of enzymes called phosphatases will dephosphorylate the tyrosine residues of the intracellular domain, deactivating the receptor.