Question

Explain why a glycine residue at position 12 of the G protein Ras is only active in the presence of growth factors but Ras with an aspartate residue at the same position is oncogenic (can cause cancer).

Answer 1

The position 12 residue in the G protein Ras is active in the presence of growth factors. An aspartate residue at the same position leads to constitutive activation of Ras and can cause cancer.

Step-by-step explanation:

The position 12 residue in the G protein Ras plays a crucial role in its activity. When glycine is present at position 12, Ras protein requires the binding of growth factors to be activated. The growth factors stimulate the exchange of GDP for GTP, which activates Ras and initiates downstream signaling pathways. However, when an aspartate residue is present at position 12, Ras becomes constitutively active, meaning it is always in the active state, leading to uncontrolled cell division and the potential development of cancer.

Answer 2

Step-by-step explanation:

At position 12 of G protein Ras there is a normal amino acid attached to it called Glycine. Which make Ras protein a highly controlled protein. However, there is another amino acid called aspartate at 12 position which make Ras vulnerable by the formation of weak GTPase enzyme activity and GTP binding. Which prevent Ras from turning off. This the reason why aspartate in oncogenic. Furthermore, weak binding of GTP has influence because its binding can not be hydrolyzed.

Reference Research Paper

Morris, K. M., Henderson, R., Suresh Kumar, T. K., Heyes, C. D., & Adams, P. D. (2016). Intrinsic GTP hydrolysis is observed for a switch 1 variant of Cdc42 in the presence of a specific GTPase inhibitor. Small GTPases, 7(1), 1-11.