· Four known Tetrahymena EF-hand proteins: Centrin, Calmodulin, TCBP 23, TCBP 25

· Low molecular weight (16 - 25 kDa) Ca²⁺ binding proteins

· Four EF Hand motifs found in each

· Contractile: change conformation in high Ca²⁺

· Localized to cell center, centrioles, basal bodies, axoneme and cell cortex

· Superfamily includes spasmin-proteins of Vorticella stalk, Stentor myonemes