ANSWER

Oligomerization can occur via fusion of a gene encoding a dimerization or oligomerization domain, such as a coiled-coil domain, onto a previously monomeric protein. The newly oligomeric protein will then associate through this oligomerization domain and potentially form new contacts in regions brought into proximity by the association (Ali & Imperiali, 2005).

Reference

Ali, M. H., & Imperiali, B. (2005). Protein oligomerization: How and why. Bioorganic & Medicinal Chemistry, 13(17), 5013-5020. https://doi.org/10.1016/j.bmc.2005.05.037