Amino acid composition of the repeats. For each amino acid, the frequency in the repeats of P < 10-10 is plotted vs. its frequency in the remainder of the proteome (rS, Spearman coefficient). Data are pooled for bacteria (n = 193) and eukaryotes (n = 49). The small diamonds at 0.05 mark the expected frequency for random distribution, the diagonal represents equal frequency in the repeats as in the remainder of the respective proteome. Complete datatables including standard deviation are provided as a supplementary file [Additional file 1].