IP 3 R can undergo post-translantional, reversible modifications. Methods such as rapid filtration or fluorescent studies of permeabilized cells lack the required precision. Three isoforms of the IP 3 R have been cloned. They have functional differences, differential tissue expression and distinct intracellular localization. Function and subcellular distribution of IP 3 R is regulated by interaction with other proteins.
Some kinases modify the receptor on amino acids which have been identified.
But several interacting proteins bind to the receptor on residues which have not been identitified and other regulatory partners remain to be recognized.