The phosphorylation state of T14 and Y15 is controlled by a dual-specificity protein kinase known as Wee1 and a pair of dual-specificity phosphatases, Cdc25B and Cdc25C (Threonine 14 is not phosphorylated in S. pombe CDK1)

TLS Online TPP Program

#Id: 9454

#Unit 4. Cell Communication and Cell Signaling

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

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#Id: 9455

#Unit 4. Cell Communication and Cell Signaling

Cytokine receptors are stably associated with one or two of the four known JAKs:

JAK1, JAK2, JAK3, and Tyk2

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#Id: 9457

#Unit 4. Cell Communication and Cell Signaling

Each members of JAK family of kinases contains:

An N-terminal domain that binds to the receptor

A C-terminal kinase domain 

A middle pseudokinase domain

TLS Online TPP Program

#Id: 9458

#Unit 4. Cell Communication and Cell Signaling

JAK kinases become activated after ligand binding and

receptor dimerization

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#Id: 9459

#Unit 4. Cell Communication and Cell Signaling

Ligand binding triggers a conformational change in the JAKs & they phosphorylate each other on a critical tyrosine in the activation loop which greatly enhances kinase activity

TLS Online TPP Program

#Id: 9461

#Unit 4. Cell Communication and Cell Signaling

Active JAK kinase phosphorylates several tyrosine residues in the receptor’s cytosolic domain and activates a STAT transcription factor that moves directly to the nucleus