The primary amino acid sequence of the Epidermal Growth Factor Receptor (EGFR) contains an invariant lysine amino acid essential for kinase activity. Substitution of this essential lysine by any other amino acid blocks the capacity of the receptor to phosphorylate targets. What stage of receptor activation is disrupted by substitution of the invariant lysine with another amino acid?

When this lysine is replaced by another amino acid:

A) EGFR is unable to activate an associated trimeric G-protein.
B) the ligand Epidermal Growth Factor (EGF) is unable to bind to EGFR.
C) docking sites for EGFR target proteins are not generated inside the cell.
D) EGFR becomes constitutively activated, that is, EGFR is always on.
E) enzymatically inactive EGFR monomers are unable to
dimerize.

The epidermal growth factor receptor (EGFR; ErbB-1; HER1 in humans) is a transmembrane protein that is a receptor for members of the epidermal growth factor family (EGF family) of extracellular proteins ligands.

The epidermal growth factor receptor is a member of the ErbB family of receptors, a subfamily of four closely related receptor tyrosine kinases: EGFR (ErbB-1), HER2/neu (ErbB-2), Her 3 (ErbB-3) and Her 4 (ErbB-4). In many cancer types, mutations affecting EGFR expression or activity could result in cancer.

Epidermal growth factor and its receptor was discovered by Stanley Cohen of Vanderbilt University. Cohen shared the 1986 Nobel Prize in Medicine with Rita Levi-Montalcini for their discovery of growth factors.

Deficient signaling of the EGFR and other receptor tyrosine kinases in humans is associated with diseases such as Alzheimer's, while over-expression is associated with the development of a wide variety of tumors. Interruption of EGFR signalling, either by blocking EGFR binding sites on the extracellular tyrosine kinase activity, can prevent the growth of EGFR-expressing tumors and improve the patient's condition.