Question

The ErbB/HER family of receptor tyrosine kinase genes are linked to many different types of human cancers. Overexpression of any of these genes would lead to an increase in the various receptors. ErbB2 encodes the HER2 protcin. This receptor does not bind any known extracellular growth factor, but it does form dimers with other growth-factor-bound HER receptors. Even modest overexpression of HER2 can alter normal cell growth regulation. Which of the following statements about receptor tyrosine kinases is correct? A. The catalytic domain is on the N-terminal end. B. Activation of the kinase requires ATP. C. Growth factor binding to the receptor triggers dimerization which activates the kinase activity. D. Active tyrosine kinase can phosphorylate other proteins but not itself. E. All of the above.

Short answer

A. The catalytic domain is on the N-terminal end. B. Activation of the kinase requires ATP. C. Growth factor binding to the receptor triggers dimerization which activates the kinase activity. D. Active tyrosine kinase can phosphorylate other proteins but not itself. E. All of the above. Answer: B. Activation of the kinase requires ATP; C. Growth factor binding to the receptor triggers dimerization which activates the kinase activity.

Step-by-step solution

Evaluate statement A

The catalytic domain of receptor tyrosine kinases is not on the N-terminal end, but it is on the cytoplasmic side of the membrane. This statement is incorrect.

Evaluate statement B

Activation of kinase does require ATP, as it is necessary for the transfer of a phosphate group during the phosphorylation process. This statement is correct.

Evaluate statement C

Growth factor binding to the receptor does trigger dimerization, which in turn activates the kinase activity. This activation allows the kinases to phosphorylate each other on specific tyrosine residues within the intracellular domain, enhancing their catalytic activity. This statement is correct.

Evaluate statement D

Active tyrosine kinase can phosphorylate itself in a process called autophosphorylation, in addition to phosphorylating other proteins. This statement is incorrect.

Evaluate statement E

Since not all statements are correct, statement E cannot be correct.

Choose the correct statement

Based on our evaluation, statements B and C are correct about receptor tyrosine kinases, so the answer is: B. Activation of the kinase requires ATP. C. Growth factor binding to the receptor triggers dimerization which activates the kinase activity.