PEP is the posterior probability of a particular PPI to be experimentally demonstrated, given that it was predicted and that both interactors were, or were not, co-localized or predicted. PEP is a probabilistic score, based on all information present in AtPINDB and is dependent on the availability of experimental data.

Predicted PPIs that has not been colocalized, experimentally or by prediction, present lower probability to be seen experimentally when compared to colocalized PPIs.