Interactions involving membranes are under-represented in the BIOGRID database. A) Fraction of the interactions identified using the method specified (below the bars) that involve at least one membrane protein. B) The total number of interactions reported by the method specified. C) Identification of ontology defined cell compartments that are over-represented by different methods for capturing interaction data. The extent of over-representation for different ontology defined cell compartments was quantified using BINGO for the specified methods. The cell compartments and methods were hierarchically clustered according to enrichment (P-values). Many of the over-represented compartments (red) relate to nuclear localization.