Figure 3. Farnesylation of p21Ras causes it to locate to the plasma membrane where it can undergo GTP loading, which is essential for signalling via the MAPK pathway.

Insulin increases activation of farnesyl transferase, which increases farnesylation of p21Ras. As a consequence, the pool of p21Ras-GTP is increased. This has the effect of amplifying growth factor signalling via the MAPK pathway. MEK, MAPK/ERK kinase.