A particular protein may or may not have allosteric sites that participate in its normal function. A chemical compound may inhibit the function of the protein by binding to a part of the protein other than its active site, even if that location plays no functional role normally. In some cases, a compound may inhibit an enzyme in a non-specific way, meaning that it does not bind in a 1:1 stoichiometry. For example, the compound may form aggregates that the protein sticks to, causing inhibition. In other cases, the compound may act as a denaturant.

@Dr. Adam:

Thank you for your wise comment. I just wonder, does the disruption cause by an inhibitor at the other part of the protein go to the same place can be called as allosteric site? Do I coin the word correctly? I bumped into a word called 'hot spot', but I couldnt distinguish both yet.

@Dr Ali:

Thanks for the links! :) It made me wonder whether I coined the word 'allosteric site' correctly or not. :/ Or maybe another suitable term should be used so that I can work on my literature search?

A hotspot is a relatively small location on the surface of a protein involved in a protein-protein interaction at which a high proportion of the binding energy is determined. Such spots are considered suitable targets for small-molecule inhibitors of the protein-protein interaction.

This is distinct from an allosteric binding site, which is typically a site other than the active site that binds a small natural regulatory ligand. However, there could be some overlap between the concepts if a protein ligand (or nucleic acid or other macromolecule) acts as an allosteric regulator.

@Dr. Adam,

Thanks! Will check it out. :)

A word of caution.  As pointed out by Gregorio Weber years ago (see Biochemistry 1972, Vol 11, p864 and  Adv Protein Chem 1975, Vol 29, p1 and the book Protein Interactions 1992, Chapman and Hall Publishers) one can easily envisage general free energy coupling between ligands bound to a protein.  If the protein is multimeric, there can also be free energy coupling between ligand binding (microassociation) and subunit interactions (macroassociations).  Any protein that binds two different ligands can express “apparent allosteary” if the binding of one ligand opposes or facilitates binding of a second ligand.  Consider the case of ANS and 3,5 dihydroxybenzoate binding to BSA.  These ligands negatively affect each other’s binding.  Hence, as Kolb and Weber showed (Biochemistry 1975, Vol 14, p4476) when one starts with a solution of BSA bound to 3,5 DHB and titrates in ANS, one can observe an apparent positive cooperativity in the binding of the ANS.  In fact, this “allosteary” is due to the fact that increasing ANS concentration leads to displacement of the 3,5 DHB which thus facilitates the binding of additional ANS ligands.  Such “apparent allotseary” is a general phenomenon and is a consequence of multiple ligand sites being able to interact with each other, or with the subunit interactions, in a positive or negative manner.  As Weber discussed, this phenomenon has also been observed for hemoglobin for the binding of oxygen and organic phosphates such as diphosphoglycerate and accounts for discrepancies in the early literature for the Hill coefficient for oxygen binding when hemoglobin had not been completely stripped of diphosphoglycerate.