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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?

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Your example of an interaction mediated by a scaffold protein is certainly one way of controlling protein interactions. This doesn't just happen in different tissues either, it is also used to fine-control the interaction of certain proteins within one cell, the most notable example for this are the kinases in the MAP pathway (see for example this paper).

Another possibility I can see is that A and B can interact, but only if (at least) one of them is modified, e.g. by phosphorylation - so the actual interaction happens with A-p and B. In a case like this it's not unlikely that the protein that modifies A is only expressed (or active) in certain tissues, which then mean A(-p) and B can only interact in these tissues.

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