Tyrosine kinase receptor

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Tyrosine kinase receptors cause the activation of tyrosine kinase enzymes[1].There are two types of tyrosine kinase receptors; receptor tyrosine kinases (RTKs) and cytokine receptors. RTKs have intrinsic tyrosine kinase activity, whereas cytokine receptors are only associated with tyrosine kinases[2]. Both are transmembrane proteins.

RTKs are the most common type of enzyme linked receptors.The intracellular region contains the tyrosine kinase enzyme; the enzyme is not very active when a ligand is not bound to the ligand binding site on the extracellular region[3]. When ligands bind to growth factor tyrosine kinase receptors, they cause a conformational change that creates a cross-linking of the extracellular regions of two RTKs (dimerization)[4]. This allows two tyrosine kinases in the intracellular domain to phosphorylate tyrosine residues on each other and become active; this results in autophosphorylation of tyrosine residues on the tyrosine kinase receptor by the activated enzymes[5]

The mechanism of cytokine receptors activating tyrosine kinases is similar to that of the RTKs. They have the same sort of stucture, but where RTKs have intrinisic kinase activity, cytokine receptors are closely associated with a JAK tyrosine kinase[6]. When a ligand binds to the extracellular receptor, conformational change is induced that brings the two intracellular JAK kinases together resulting in autophosphorylation, the same way as with RTKs above[7]

In both cases, the phosphorylated tyrosine residues on the receptor act as docking stations for other proteins involved in signalling pathways, for example the Ras pathway [8].

References

  1. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.723.
  2. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.723.
  3. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.724.
  4. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.724.
  5. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.724.
  6. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.728.
  7. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.729.
  8. Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., Amon, A., Scott, M. P., 2013, Molecular Cell Biology. 7th end. New York : W.H. Freeman and Company, p.734.
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