If Lk <Lk0 and DLk is <0 means negative, then the DNA is said to be “negatively supercoiled.”

TLS Online TPP Program

#Id: 9604

#Unit 4. Cell Communication and Cell Signaling

NGF, PDGF, FGF, EGF, insulin are RTK ligands, which trigger proliferation of cells.

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#Id: 9605

#Unit 4. Cell Communication and Cell Signaling

The cytosolic domain of RTKs contains an intrinsic protein tyrosine kinase domain.

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#Id: 9606

#Unit 4. Cell Communication and Cell Signaling

Cytosolic kinase domain of an RTK contains a flexible domain termed activation loop. 

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#Id: 9607

#Unit 4. Cell Communication and Cell Signaling

In resting state,  the activation loop is not phosphorylated and assumes a conformation that blocks kinase activity.

In insulin receptor, it prevents binding of ATP. 

In FGF receptor, it prevents binding of substrate.

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#Id: 9608

#Unit 4. Cell Communication and Cell Signaling

For most, but not all, RTKs, the weakly active kinase in each subunit is phosphorylate a key tyrosine in the activation loop of the other subunit (trans-phosphorylation)

TLS Online TPP Program

#Id: 9609

#Unit 4. Cell Communication and Cell Signaling

Phosphorylation leads to a conformational change in the activation loop that unblocks kinase active site by reducing the Kd for ATP or the substrate to be phosphorylated.