15. Refer to the figure below. of cel O o Cytokine nside of coll Dimerization Nu

Question

15. Refer to the figure below. of cel O o Cytokine nside of coll Dimerization Nucleus mRNA The figure shows a signal transduction pathway involving two proteins found in the cytoplasm-JAK and STAT. Based on this figure, what are the roles of JAK and STAT in this pathway? JAK is a protein kinase and STAT is a G protein. O JAK is a G protein and STAT is a transcription factor O JAK is a protein kinase and STAT is a transcription factor O JAK is a G protein and STAT is adenylyl cyclase O JAK is a transcription factor and STAT is a GTPase.

Explanation / Answer

15. JAK protein stands for Janus Kinase protein. These are protein tyrosine kinases. They form an integral component of receptor units of the cytokines. They also perform a key role in activation of enzymes. They form the preliminary step which is essential for initiation of signalling cascade. JAKs are known to function in development of embryos, inflammatory response, development of immunity etc.

STATs are basically the members of the signal tranducer family. They also function as transcription factors. Hence, they play a dual role in signal transduction as well as in initiation of transcription.

In this figure, JAKs are brought into close proximity upon ligand binding. This is achieved through oligomerization followed by autophosphorylation which results in the activation of JAK kinases. They then phosphorylate tyrosine residues. The phosphorylation results in creation of docking sites for STATs. Now, SH2 domain and C terminal domain are phosphorylated to create STAT dimers. They are then translocated to nucleus where they bind to palindromic sequence and help in initiation of transcription.

Hence, JAK is a protein kinase and STAT is a transcription factotr

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.