Oligomerization enables cooperativity between multiple binding sites, a property referred to as allostery or allosteric regulation of enzymes (yet again, single polypeptide, multi-domain proteins show allosteric behavior). (whatislife.com)

The sequential model of allostery holds that subunits are not connected in such a way that a conformational change in one induces a similar change in the others. Thus all enzyme subunits need not exist in the same conformation. (bio-medicine.org)

It also follows that allostery is common and that homologous proteins can have different allosteric mechanisms. (nature.com)