Figure 3.

Stereoview of the evolution of the switch I region. The backbone positions of the switch I region (in darker gray) obtained at different times are shown superimposed on each other; the thickness (darkness) of the lines increases during the transition. The GDP nucleotide is represented by a ball-and-stick model and the side chains of Tyr-32 and Tyr-40 are included for comparison with Fig. 1. The part of the α-carbon trace that overlaps with the Tyr-32 side chain is omitted for clarity.