STRING v9.1: protein-protein interaction networks, with increased coverage and integration

Complete knowledge of all direct and indirect inter-actions between proteins in a given cell would represent an important milestone towards a com-prehensive description of cellular mechanisms and functions. Although this goal is still elusive, consid-erable progress has been made—particularly for certain model organisms and functional systems. Currently, protein interactions and associations are annotated at various levels of detail in online resources, ranging from raw data repositories to highly formalized pathway databases. For many applications, a global view of all the available inter-action data is desirable, including lower-quality data and/or computational predictions. The STRING databas