Fractions of human and E. coli TFs occupied by structural domains and ID regions. a) Overall statistics of structural domains and ID regions in human and E. coli TFs. The red, orange, and gray sectors represent the fractions of residues in known structural domains, cryptic domains, and ID regions, respectively. b) Histograms of TFs sorted according to fraction ranges occupied by structural domains and cumulative frequencies. The red bars show the frequency, while the black lines connecting dots represent the cumulative frequencies. The fractions of structural domains are plotted along the x axis. The scale on the left is for the number of TFs, while the right scale is for the cumulative frequency.