An interaction is inferred from the biochemical effect of one protein upon another, for example, GTP-GDP exchange activity or phosphorylation of a substrate by a kinase. The bait protein executes the activity on the substrate hit protein. A Modification value is recorded for interactions of this type with the possible values Phosphorylation, Ubiquitination, Sumoylation, Dephosphorylation, Methylation, Prenylation, Acetylation, Deubiquitination, Proteolytic Processing, Glucosylation, Nedd(Rub1)ylation, Deacetylation, No Modification, Demethylation.

Interaction inferred from two proteins that co-localize in the cell by indirect immunofluorescence only when in addition, if one gene is deleted, the other protein becomes mis-localized. Also includes co-dependent association of proteins with promoter DNA in chromatin immunoprecipitation experiments.

An interaction is inferred when close proximity of interaction partners is detected by fluorescence resonance energy transfer between pairs of fluorophore-labeled molecules, such as occurs between CFP (donor) and YFP (acceptor) fusion proteins.

An interaction is inferred between proteins in vitro. This can include proteins in recombinant form or proteins isolated directly from cells with recombinant or purified bait. For example, GST pull-down assays where a GST-tagged protein is first isolated and then used to fish interactors from cell lysates are considered reconstituted complexes (e.g. PUBMED: 14657240, Fig. 4A or PUBMED: 14761940, Fig. 5). This can also include gel-shifts, surface plasmon resonance, isothermal titration calorimetry (ITC) and bio-layer interferometry (BLI) experiments. The bait-hit directionality may not be clear for 2 interacting proteins. In these cases the directionality is up to the discretion of the curator.

Bait protein expressed as a DNA binding domain (DBD) fusion and prey expressed as a transcriptional activation domain (TAD) fusion and interaction measured by reporter gene activation.