Ras is a GTP binding protein that acts to relay signals from a receptor to diffe
ID: 57041 • Letter: R
Question
Ras is a GTP binding protein that acts to relay signals from a receptor to different pathways. It is always bound to the plasma membrane. How is it activated?
Ligand binding results in phosphorylation of Ras
Ligand binding results in phosphorylation of a GEF
Ligand binding results in phosphorylation of the receptor and recruitment of a GEF
Ligand binding results in phosphorylation of the receptor and recruitment of a GAP
Which of the following are NOT TRUE about tyrosine kinase associated receptors?
they bind to tyrosine kinases
they have tyrosine kinase domains
the alpha interferon receptor is an example of a tyrosine kinase associated receptor
ligand binding results in phosphorylation of the cytoplasmic tails of the receptors on tyrosines
Ligand binding results in phosphorylation of Ras
B.Ligand binding results in phosphorylation of a GEF
C.Ligand binding results in phosphorylation of the receptor and recruitment of a GEF
D.Ligand binding results in phosphorylation of the receptor and recruitment of a GAP
Which of the following are NOT TRUE about tyrosine kinase associated receptors?
A.they bind to tyrosine kinases
B.they have tyrosine kinase domains
C.the alpha interferon receptor is an example of a tyrosine kinase associated receptor
D.ligand binding results in phosphorylation of the cytoplasmic tails of the receptors on tyrosines
Explanation / Answer
Ras is a GTP binding protein and its binding to receptor and GTP activates the guanine nucleotide exchange factors (GEF) and GTPase activating proteins (GAP). The binding of ligand to receptor results in recruitment of GAP by the phosphorylation of receptors. Hence, option D is correct.
Tyrosine kinase associated receptors after binding with the ligand undergo phosphorylation of tyrosine residues in the phosphorylation lip near the catalytic site resulting in the confirmational change that helps in binding of ATP to the receptors. The receptor kinase activity then phosphorylates other sites in the cytosolic domain. Hence, option D is correct.
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