Figure 3From: Amino acid composition in endothermic vertebrates is biased in the same direction as in thermophilic prokaryotesAmino acid usage differs between endothermic and ectothermic vertebrates. Distribution of amino acid usage bias, ERK, across proteins for endothermic vertebrates (mammals, birds) and ectothermic ('cold-blooded') vertebrates (reptiles, amphibia, fish). ERK is significantly increased in endothermic relative to ectothermic animals (Wilcoxon rank sum test: p < 10-15). See Additional file 1: Supplemental Figure S4 for a correlated alternative measure of amino acid usage bias.Back to article page