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. 2002 Mar 19;99(6):3575–3580. doi: 10.1073/pnas.052209199

Figure 1.

Figure 1

Schematic representation of the structure of GTP-bound (Left) and GDP-bound (Right) Ras protein (generated by the molecular graphics program vmd (22). The major conformational difference between the two structures involves the switch II region composed of the α2 helix and the L4 loop. In the case of Ras/GDP, the final turn of the α2 helix in contact with the L4 loop is unwound, whereas L4 is highly disordered. To gauge the force-generating ability of Ras, a harmonic spring, of stiffness constant k, is inserted between the COM of residues Gly-60 and Tyr-32 (see text).