Characteristic conserved residues within distinct FY-pivot GTPases of known structure. FY-pivot GTPases from distinct families or subfamilies were structurally aligned against Sec4p using the CE program (Shindyalov and Bourne 2001); alignment errors were corrected based on direct structural observations. This alignment was then used as the ‘family set’ alignment for CHAIN analysis (see Methods) to obtain this two-tier hierarchical alignment. The histograms and highlighted residues correspond to category-specific selective constraints, as described in Figure 2 B,C. (A) Conserved residues characteristic of P-loop GTPases. The structural regions shown in Figure 2 E and in Figures 4 F5 F6 F7 F8 F9 are indicated at thetop. (B) Conserved residues characteristic of FY-pivot GTPases. Key residues shown in Figure 4 and in Figures 5 F6 F7 F8 F9for Sec4p and Ran, respectively, are indicated at the bottom.
