Figure 5

Active site propensity of amino acids and comparison with their natural frequencies. (A) For each type of amino acids, the frequencies of occurrence in the active and non-active sites were calculated. The ratio between them is defined as the active site propensity (ordinate). (B) Natural (UniProt) frequency of occurrence vs. active site propensity for each type of amino acid. Less frequent amino acids tend to have a higher active site propensity, and vice versa, in accord with the histograms in Figure 4. This effect becomes more pronounced at the level of 3-grams.