STRING is a database of known and predicted protein interactions. The interactions include direct (physical) and indirect (functional) associations. They are derived from Genomic Context, High-throughput Experiments (Conserved), Coexpression, Previous Knowledge. STRING quantitatively integrates interaction data from these sources for a large number of organisms, and transfers information between these organisms where applicable. The database currently covers 2,590,259 proteins from 630 organisms. Registration not required.