The main difference between G-protein-linked and enzyme-linked receptors is that G-protein-linked receptors have seven transmembrane segments, whereas enzyme-linked receptors have only one segment.
G-protein-linked and enzyme-linked receptors are the two types of receptors with a ligand-binding domain. They are transmembrane proteins.
Key Areas Covered
1. What are G-Protein Linked Receptors
– Definition, Facts, Features
2. What are Enzyme-Linked Receptors
– Definition, Facts, Features
3. Similarities Between G-Protein Linked Receptors and Enzyme-Linked Receptors
– Outline of Common Features
4. Difference Between G-Protein Linked Receptors and Enzyme-Linked Receptors
– Comparison of Key Differences
5. FAQ – G-Protein Linked Receptors and Enzyme-Linked Receptors
– Answers to frequently asked questions
Key Terms
Enzyme-Linked Receptors, G-Protein Linked Receptors
What are G-Protein Linked Receptors
The G-protein-coupled receptors (GPCRs) are the largest class of membrane proteins in eukaryotes, which mediate most of the physiological responses of hormones, neurotransmitters, and environmental stimulants. They are also responsible for vision, sense of smell and taste. One of the critical features of GPCRs is the presence of seven membrane-spanning α-helices interconnected by alternative intracellular and extracellular loop regions.
Figure 1: G-Protein Linked Receptors
Furthermore, When the G-protein-coupled receptor is not bound to an agonist, it remains inactive. Upon binding a ligand/agonist such as hormones or neurotransmitters, the GPCR undergoes a conformational change, activating its GEF domain. Upon activation, the Gsα domain dissociates from the GPCR-G protein complex and binds to the effector enzyme on the cell membrane to activate it. The hydrolysis of GTP into GDP in the Gsα domain dissociates from the effector enzyme, deactivating the enzyme.
What are Enzyme-Linked Receptors
Enzyme-linked receptors are a group of multi-subunit transmembrane proteins with intrinsic enzyme activity on the intracellular domain or directly associated with an intracellular enzyme. Significantly, the extracellular and intracellular domains of the enzyme-linked receptors are large. However, the membrane-spanning region is composed of a peptide strand with a simple alpha-helical region. Moreover, the intracellular enzyme activates upon ligand binding to the extracellular domain. Then, the signal transmits through the membrane and activates the enzyme.
Figure 2: Enzyme-Linked Receptors
Also, there are five main types of enzyme-linked receptors. They are receptor tyrosine kinase, receptor serine/ threonine kinase, receptor guanylyl cyclases, tyrosine-kinase-associated receptors, and receptor tyrosine phosphatases. Growth factors, hormones, and cytokines also serve as ligands to the enzyme-linked receptors and regulate cell growth, proliferation, and differentiation.
Similarities Between G-Protein Linked Receptors and Enzyme-Linked Receptors
- G-protein-linked receptors and enzyme-linked receptors are two types of cell surface receptors.
- They are transmembrane proteins with a ligand-binding domain.
- This ligand molecule converts the extracellular signal into the intracellular signal.
- Hormones can serve as ligands to both types of receptors.
Difference Between G-Protein Linked Receptors and Enzyme-Linked Receptors
Definition
G-protein linked receptors refer to proteins in the cell membrane that bind extracellular substances and transmit signals from these substances to an intracellular molecule called a G protein. In contrast, enzyme-linked receptors refer to the receptors for many growth factors, cytokines, and hormones and have a significant role in regulating cell growth, proliferation, and differentiation.
Structure
G-protein-linked receptors have seven transmembrane segments, while enzyme-linked receptors have only one segment.
Function
G-protein-linked receptors bind a ligand and activate G protein, a membrane protein, which then interacts with an ion channel or in the membrane. In contrast, enzyme-linked receptors are cell surface receptors that contain an intracellular domain associated with an enzyme.
Role
G-protein-linked receptors regulate physiological responses, while enzyme-linked receptors regulate growth, proliferation, and differentiation.
FAQ: G-Protein Linked Receptors and Enzyme-Linked Receptors
What is the difference between an enzyme and a receptor?
An enzyme is a catalyst, while the receptor sits on a cellular membrane. Also, an enzyme has a catalytic action. It has energetically and conformationally different states.
What is the difference between protein kinase receptors and G-protein-linked receptors?
Receptor tyrosine kinases can undergo a single ligand binding event to trigger many pathways.
What are the two types of receptors, and how are they different?
There are two types of receptors: intracellular and extracellular. Extracellular receptors are cell surface receptors that occur on the plasma membrane. In contrast, intracellular receptors occur inside the cell.
Conclusion
In brief, G-protein-linked receptors and enzyme-linked receptors are two types of cell surface receptors. They are transmembrane proteins with a ligand-binding domain. G-protein-linked receptors have seven transmembrane segments. G-protein-linked receptors bind to a ligand and activate G protein interacting with an ion channel. In comparison, enzyme-linked receptors have only one segment. Also, it contains an intracellular domain associated with an enzyme. Therefore, the main difference between G-protein and enzyme-linked receptors is their structure and function.
References:
- Libretexts. (2023, January 17). 3.4A: Types of receptors. Medicine LibreTexts.
- Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. Signaling through Enzyme-Linked Cell-Surface Receptors.
Image Courtesy:
- “Activation protein kinase C.” By Yikrazuul – Own Work (CC BY SA 3.0) via Commons Wikimedia
- “Figure 09 01 07” By CNX OpenStax (CC BY 4.0) via Commons Wikimedia
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