Conservation of interacting proteins by degree. (a) Each protein in the yeast interaction network was examined for orthologous proteins in the five higher eukaryotes, and binned according to degree. The proportion of each bin with orthologous proteins is shown. The linear trend shows the strong positive correlation (Spearman's rank r = 0.52, P = 2.8 × 10-11) between yeast and human proteins. (b) The proteins in the human interactome were compared against all five lower eukaryotes, and binned according to degree. This trendline also shows a strong correlation against yeast (Spearman's rank r = 0.50, P = 3.9 × 10-4), which is similar for worm and rat, and there is a weak (non-significant) correlation to fly. There was a weak negative correlation in mouse (Spearman's rank r = -0.02); however, the overall conservation was high, likely biasing this measurement.