Figure 3.

Ras dimerization and reorientation affect access to binding partners. (A) Several dimer interfaces for Ras have been proposed. The most prominent ones center around either helices α4 and α5 or helices α3 and α4. Dimer affinities are expected to be weak, even if Ras concentration is effectively elevated in the 2D membrane. (B) Reorientation of Ras on the membrane may occlude the effector lobe, thus restricting access to binding partners such as effectors. Reorientation and dimerization employ overlapping secondary structural elements, such as helix α4. Therefore, it can be expected that they mutually affect one another.