Solvent accessibility of phosphorylatable residues. The plots show the distributions of the percentage of solvent accessibility of the (a) serine/threonine and (b) tyrosine side chains in the structures, as calculated by NACCESS . The cyan and red columns correspond to the distributions for all potential and known phosphorylated residues, respectively, whereas the yellow columns are controls summarizing the solvent accessibility of all amino acids. Exposed terminal regions were not included in the calculations. These distributions were identical to that calculated from the templates or from models sharing at least 80% identity to the templates, indicating that, overall, the modeled conformations of the residues holding the phosphosites are expected to be accurate.