Difference Between G Protein Coupled Receptors and Receptor Tyrosine Kinases

The key difference between G protein coupled receptors and receptor tyrosine kinases is that the G protein coupled receptors can trigger only one cell response from a single ligand binding while the receptor tyrosine kinases can trigger many cell responses from a single ligand binding.

Receptors are proteins that involve in the cell signalling process. They can be intracellular receptors as well as cell surface receptors. Cell surface receptors locate on the surfaces of the cells and receive the signals and pass them to the cell interior to react accordingly. There are two main types of cell surface receptors; namely, they are the G protein-coupled receptors and receptor tyrosine kinases. They are transmembrane proteins. G protein coupled receptors contain seven transmembrane domains, and they associate with G proteins. On the other hand, receptor tyrosine kinases are enzyme-linked receptors that associate with ATP and enzyme kinases.

CONTENTS

1. Overview and Key Difference
2. What are G Protein Coupled Receptors
3. What are Receptor Tyrosine Kinases
4. Similarities Between G Protein Coupled Receptors and Receptor Tyrosine Kinases
5. Side by Side Comparison – G Protein Coupled Receptors vs Receptor Tyrosine Kinases in Tabular Form
6. Summary

What are G Protein Coupled Receptors?

G protein coupled receptors are a type of transmembrane proteins. As the name suggests, these receptors work with the G proteins that associate with GTP. GTP is a similar molecule to ATP that provides energy to G proteins to work. Once a ligand binds with the receptor, the shape of the receptor changes in a way that it can interact with the G protein.

The inactive form of the G protein transforms into the active form and divides into two pieces (alpha and beta subunits) by converting GTP into GDP and utilizing the released energy. These subunits then separate from the G protein coupled receptor and interact with other proteins to trigger cell responses. Structurally, G protein coupled receptors have seven transmembrane domains that are spanning across the membrane.

What are Receptor Tyrosine Kinases?

Receptor tyrosine kinases are a type of receptor proteins that involve with most of the cell signalling pathways. As the name implies, they are kinase enzymes. Kinase is an enzyme that catalyzes the transfer of phosphate groups to a substrate. These receptors contain tyrosine kinases that transfer a phosphate group from ATP to tyrosine. Receptor tyrosine kinase has two similar monomers.

Once a signalling molecule binds with the binding site of the receptor, two monomers come together and form a dimer. Then, kinases phosphorylate ATP and add phosphate groups to each of the six tyrosines. Hence, dimer becomes phosphorylated, which is a fully activated tyrosine kinase. Activated tyrosine kinase sends signals to other molecules of the cell and mediates signal transmission. The most important characteristic of receptor tyrosine kinase is, it can activate multiple signalling pathways and when it activates, it can create multiple cell responses at once.

What are the Similarities Between G Protein Coupled Receptors and Receptor Tyrosine Kinases?

• They are receptors that involve cell signalling pathways.
• Structurally, they are protein molecules.
• Moreover, they are transmembrane proteins.
• Furthermore, they are cell surface receptors.
• Initially, they remain inactive and then become active upon binding a ligand to the receptor.

What is the Difference Between G Protein Coupled Receptors and Receptor Tyrosine Kinases?

G protein coupled receptors and receptor tyrosine kinases are two types of cell surface receptors that mediate cell signalling pathways. G protein coupled receptors associate with G proteins and GTP.  On the other hand, receptor tyrosine kinases are enzyme-linked receptors associated with tyrosine and ATP. Therefore, this is a key difference between G protein coupled receptors and receptor tyrosine kinases. Furthermore, single ligand binding triggers multiple cell responses by receptor tyrosine kinases while only one cell response originates from G protein coupled receptors upon single ligand binding. Thus, this is another key difference between G protein coupled receptors and receptor tyrosine kinases.

The following infographic present more information on the difference between G protein coupled receptors and receptor tyrosine kinases.

Summary – G Protein Coupled Receptors vs Receptor Tyrosine Kinases

G protein coupled receptors and receptor tyrosine kinases are two common cell surface receptors. G protein coupled receptors contain seven transmembrane domains while receptor tyrosine kinases have two similar monomers. When a ligand binds to the receptor, in G protein coupled receptors, a G protein is activated. But, in receptor tyrosine kinases, a tyrosine dimer is formed and phosphorylated.

Furthermore, G protein coupled receptors can trigger only one cell response when a ligand binds to the receptor. On the other hand, receptor tyrosine kinase can trigger multiple responses when a ligand binds to the receptor. Thus, this summarizes the difference between G protein coupled receptors and receptor tyrosine kinases.

Reference:

1.“Ligands & Receptors.” Khan Academy, Khan Academy. Available here  
2.“G Protein-Coupled Receptor.” Wikipedia, Wikimedia Foundation, 12 Nov. 2018. Available here  

Image Courtesy:

1.”G-protein-coupled receptor”By Bensaccount, Mifter. (Public Domain) via Commons Wikimedia  
2.”VEGF receptors”By Häggström, Mikael (2014). “Medical gallery of Mikael Häggström 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 2002-4436. (Public Domain) via Commons Wikimedia