Contribution of Weak Homologs. Contribution of weak homologous PPIs to the overall classification performance of the scoring scheme. The gray ROC curve (squares) represents the original performance of the scoring scheme (considers all homologous PPIs with an E-value up to 10). The red ROC curve (crosses) illustrates the performance of the scoring scheme when only homologs with an E-value up to 1 are examined, and the blue curve (triangles) ignores all homologs with an E-value above 10-10. GSP PPIs were taken from the Combined data set, GSN PPIs comprised all PPIs from the Random data set. The area under the curve (AUC) is 80%, 85% and 86% for E-values 10-10, 1, and 10, respectively.