Conservation of protein–protein interactions between homologous protein pairs. (A,B) Relationships between V and J_I. (C,D) Relationships between V and J_E.(E,F) Relationships between L and J_E. (A,C,E) Calculated based on the results from worm-yeast mapping. (B,D,F) The weighted average obtained when the interactions in all four organisms (i.e., S. cerevisiae, C. elegans, D. melanogaster, and H. pylori) were mapped onto yeast. (A) Low: J_I ≤ 10%; Medium: 20% ≤ J_I ≤ 30%; High: J_I ≥ 40%. (C,D) Low: 10^–40 ≤ J_E ≤ 10^–10; Medium: 10^–100 ≤ J_E ≤ 10^–50; High: J_E ≤ 10^–110. Error bars represent 95% CI calculated by a resampling algorithm (see Supplemental material).