Suppose protein A and B is both abundant in tissue X an tissue Y. Will A and B interact in X but not interact in Y?
I guess A and B could be biomarkers of a certain disease, and in the pathological tissues their amount remains relatively unchanged but no longer interact, thus losing their functionality and causing the disease.
One possible condition would be that A and B don't interact directly but require a third protein C to act as the scaffold to form the complex A-C-B. So when C is expressed in tissue X but not in Y, we would observe this phenomenon.
Are there other mechanisms or examples?