The tubulin superfamily includes five distinct families, the alpha-, beta-, gamma-, delta-, and epsilon-tubulins and a sixth family (zeta-tubulin) which is present only in kinetoplastid protozoa. The epsilon-tubulins which are widespread but not ubiquitous among eukaryotes play a role in basal body/centriole morphogenesis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",