Integration of public protein-protein interaction data. SynechoNET integrates four protein-protein interaction databases that contain mutually complementary as well as redundant information. (a) PSIMAP provides protein-protein interaction data based on PDB, SCOP, and PSI-BLAST search. (b) Likewise, iPFAM provides protein-protein interaction data based on PDB, MSD, and PFAM. (c) On the other hand, InterDom is a collective database of putative interacting protein domains from experimental data, domain fusion, protein complex, and scientific literature. (d) Similarly, STRING integrates protein-protein interaction data from various data sources such as genomics context, curated interaction databases, conserved co-expression, and scientific literature. Furthermore, it expands those protein-protein interactions through orthology transfer originally based on the COG database.