In DNA polymerase, the nucleotide-binding pocket cannot accommodate a 2’-OH on the in-coming nucleotide. This space is occupied by two amino acids that make van der Waals contacts with the sugar ring. Changing these amino acids to other amino acids with 

TLS Online TPP Program

#Id: 9448

#Unit 4. Cell Communication and Cell Signaling

Receptor Homodimerization 

Cytokines (erythropoietin) activate receptors by forming dimers of two identical cytokine receptor proteins

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#Id: 9450

#Unit 4. Cell Communication and Cell Signaling

Receptor hetero-dimerization or hetero-oligomerization 

Other cytokines (interleukins and interferons) bind simultaneously to two or more different cytokine receptors

TLS Online TPP Program

#Id: 9451

#Unit 4. Cell Communication and Cell Signaling

The extracellular domain of cytokine receptors are constructed of two subdomains, each contains seven conserved β strands folded together

TLS Online TPP Program

#Id: 9452

#Unit 4. Cell Communication and Cell Signaling

In cytokine receptors, 

the receptor and kinase are separate polypeptides, encoded by different genes, yet are bound tightly together.

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#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