Studies of families in which multiple members show signs of insulin resistance h
ID: 64041 • Letter: S
Question
Studies of families in which multiple members show signs of insulin resistance have identified inherited mutations in the insulin receptor gene. One such inhereited mutation, Val 382 Phe, in which a valine amino acid at position 382 is substitued by a phenylalanine amino acid, prevents the mutant insulin receptor protein from being properly transported to the plasma membrane.
Why is the presence of the insulin receptor at the plasma membrane essential for proper signal transduction?
The mutant protein is produced by a mutation in the coding strand of the insulin receptor gene from a G to a T. Explain how this mutation could cause a change of an amino acid from valine to phenylalanine in the protein transcribed and translated from this gene.
Explanation / Answer
When there is a rise in blood sugar level, insulin acts on the glucose uptake from blood through cellular membrane for its metabolization. Binding of insulin to the receptor present on the cell membrane activates a specific protein tyrosine kinase by changing quaternary structure of receptor. The tyrosin activity causes the activation or phosphorylation of enzymes. Whereas activation of protein kinase leads to activation of additional protein kinases.