Figure 3. Distribution of Amino Acids by Protein Length Across Human Proteome.

The counts of each amino acid as a function of relative length are shown with each letter corresponding to the appropriate amino acid. Each protein was divided into 100 segments and the total count of each amino acid in each segment was summed across the proteome. For example, a 200 amino acid long protein with a serine in position 3 and a lysine in position 4 would add a count of one S and one L in the 2% bin along the horizontal axis. Proline, P, peaks in prevalence at the 2% of length position, with 8,215 prolyl residues of a total of 108,671 amino acids (7.6% proline). The vertical axis was normalized to reflect a percent frequency.