Tubulin family members are globular proteins important in the assembly of microtubules. Microtubules are structural components that play important roles in mitosis, cytokinesis and vesicle transport. TPPP (Tubulin polymerization-promoting protein), also known as p24 and p25, is a widely expressed 219 amino acid protein found in the perinuclear region of the cytoplasm. TPPP may form dimers and functions in polymerizing tubulin into double-walled tubules, polymorphic aggregates, or stabilized