Figure 2.

Analysis of 970 loop mutants. a) Letter sizes are scaled to reflect the relative abundance of that nucleotide in the selected pool at each position. Covariation between nucleotides is indicated by solid lines. Positions where nucleotide identity significantly correlates with function (ANOVA) are boxed. The red and blue colors indicate the nucleotides involved in formation of the two stacked triples seen in the crystal structure. b) Structure of the 970 loop.²⁵ Stacked nucleotides are colored corresponding to the coloring in a).