Repeated use of interacting domain-pairs in PPI networks. For each organism, the number of occurrences of each DDI in the PPI network was counted. The histogram shows the frequency of PPIs that were attributed to DDIs used only once, twice, and so on. The frequency is computed out of all the PPI-DDI mappings. DDI, domain-domain interaction; PPI, protein-protein interaction.
Itzhaki et al. Genome Biology 2006 7:R125 doi:10.1186/gb-2006-7-12-r125