Functional coverage of protein-protein interactions. The fraction of known functional annotations that can be suggested through BLAST homology search; and the additional annotations that can be suggested through: 1) direct protein interactions (PPI) and 2) indirect protein interactions. A range of BLAST E-value cutoffs between 1 to 1e-10 is used. BLAST is performed on sequences from the gene ontology database. Proteins with very close homologs (E-value ≤ 1e-25) are excluded from analysis. The top row shows the results from S. cerevisiae, and the bottom row shows the results from D. melanogaster. The three columns depict results on the biological process (left), molecular function (center) and cellular component (right) categories of the Gene Ontology.