Functional links between proteins can often be inferred from genomic 
associations between the genes that encode them: groups of genes that are 
required for the same function tend to show similar species coverage, are often 
located in close proximity on the genome (in prokaryotes), and tend to be 
involved in gene-fusion events. The database STRING is a precomputed global 
resource for the exploration and analysis of these associations. Since the three 
types of evidence differ conceptually, and the number of predicted interactions 
is very large, it is essential to be able to assess and compare the significance 
of individual predictions. Thus, STRING contains a unique scoring-framework 
based on benchmarks of the different types of associations against a common 
reference set, integrated in a single confidence score per prediction. The 
graphical representation of the network of inferred, weighted protein 
interactions provides a high-level view of functional linkage, facilitating the 
analysis of modularity in biological processes. STRING is updated continuously, 
and currently contains 261 033 orthologs in 89 fully sequenced genomes. The 
database predicts functional interactions at an expected level of accuracy of at 
least 80% for more than half of the genes; it is online at 
http://www.bork.embl-heidelberg.de/STRING/.