Chapter 16, Problem 1RTC

Summary Introduction

To write:

The three common features of the activation of cytokine receptors and receptors tyrosine kinases. A difference between these receptors according to enzymatic activity.

Introduction:

Cytokine receptors are the cell-surface glycoproteins which bind to the cytokines and transduce their signals. These receptors allow the cells to communicate with their extracellular environment. It is done by giving a response to signals produced in the surroundings or in different parts of an organism. Tyrosine kinase (an enzyme) which helps in the phosphate group transfer from the ATP molecule to a protein in the cell. Its main role is as an "on" or "off" switch in most of the cellular functions.

Explanation of Solution

The three common features of the activation of cytokine receptors and receptors tyrosine kinases are as follows:

1. Both cytokine receptors and the receptor's tyrosine kinases (RTKs) help in the formation of functional dimers after binding with their ligands. After the dimerization process, the poorly active cytosolic kinase usually phosphorylates the other one on a definite tyrosine in the activation site.

2. In this phosphorylation, the kinase is activated which again phosphorylates the second kinase of the dimer. It also happens in other tyrosine residues of the receptor.

3. Both the RTKs and cytokine receptors act as the reducing locations for the signaling molecules. These signaling molecules link to these phospho-tyrosine sites.

A big difference between the RTKs and cytokine receptors is:

The RTK is itself a tyrosine kinase, while the cytokine receptor does not possess catalytic activity. Rather cytokine receptor is linked with a JAnus Kinase (JAK kinase).

Conclusion

Thus, the common features include the phosphorylation the activation of cytokine receptors and receptors tyrosine kinases. The difference between these two is that the cytokine receptor does not possess catalytic activity while RTK is an enzyme which possesses this activity.