In a series of experiments mutant form* of a receptor tyrosine kinase are introd
ID: 170099 • Letter: I
Question
In a series of experiments mutant form* of a receptor tyrosine kinase are introduced into cells in large amounts The cells still express their own normal form of the receptor. a. What would be the consequence of introducing 10 times the number of mutant receptor tyrosine kinases that are musing the extracellular domain (the part of the protein outside the cell). The part of the receptor that is inside the cell is normal. What would be the consequence of introducing 10 times the number 10 mutant receptor tyrosine kinases that are lacking the intracellular domain (the part of the protein inside the cell). The part of the receptor that is outside the cell is normal.Explanation / Answer
a) Normally receptor tyrosine kinases contain two domains - receptor binding domain and ligand binding domain. The rceptor binding domain required dimerization so that cross phosphorylation takes place to initiate the signalling and ligand binding domain is thus activate to propagate the signal. When mutant receptor tyorisne kinases are added in excess to a cells with inactive kinase domain, the dimerization of receptor takes place but cross phosphorylation does not occur as the external binding domain is missing. This results in blocking of signals in normal receptors. This process is known as dominant-negative inhibition. It is useful to study the function of normal receptors.
b) The phosphorylated mutant receptor tyrosine kinases lacking internal domains may activate several down stream proteins like Ras proteins in the signal cascade. This may lead to irregular cell proliferation and may result in causing cancer.
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