Over-representation of drug targets over a degree ranking of proteins. Proteins were grouped into bins according to their degree. The width of each bin represents the number of proteins in that bin while the height (−log of the p-value of the hypergeometric test) represents how over-represented drug targets are in that bin. Each bin contains at least 200 proteins. Over-represented bins (p-value < 0.05) are highlighted in red. The number of drug targets in each bin is indicated at the top of each bar. Drug targets are over-represented in high-degree bins and some middle-degree bins for the full PIN (a), while over-representation is observed only in the highest degree bin of BioGrid (b) and not at all in the Rual and Stelzl (c) or Rual-only (d) data sets.