Flexibility. Two-dimensional histograms comparing structural conservation and flexibility for pocket clusters of the different families in the data set. The panels on the left display the values for pocket clusters 1 to 3 of 1,128 distinct protein families and the right panels show the distribution for clusters containing the majority of active sites for 229 protein families. The top panels show the percentage of pockets that were significantly flexible when compared to the rest of the structure, while the bottom panels show the percentage of pockets found to be significantly rigid (less flexible) than the rest of the corresponding protein structure. These plots only include protein families with at least five representative structures.