The diameter of a typical α helix is about 12 Å, which matches the 12 Å wide and 6–8 Å deep major groove of B-form DNA. 

TLS Online TPP Program

#Id: 1361

#Unit 4. Cell Communication and Cell Signaling

Cytokine receptors activate tyrosine kinases in which receptor and kinase are separate polypeptides.

TLS Online TPP Program

#Id: 1362

#Unit 4. Cell Communication and Cell Signaling

In cytokine receptors, the tightly bound kinase is known as a JAK kinase.

TLS Online TPP Program

#Id: 1363

#Unit 4. Cell Communication and Cell Signaling

JAK kinases become activated after ligand binding and receptor dimerization.

TLS Online TPP Program

#Id: 1364

#Unit 4. Cell Communication and Cell Signaling

Phosphorylation of the activation loop leads to a conformational change in the JAK kinase that enhances the affinity of the enzyme for ATP & increasing kinase activity.

TLS Online TPP Program

#Id: 1365

#Unit 4. Cell Communication and Cell Signaling

JAK kinases phosphorylate several tyrosine residues on the cytosolic domain of the cytokine receptor.

TLS Online TPP Program

#Id: 1366

#Unit 4. Cell Communication and Cell Signaling

Phosphotyrosines function as docking sites for STAT proteins.