minusend

Minus end refers to the end of a cytoskeletal filament from which growth or depolymerization proceeds more slowly and toward which certain motor proteins move. The term is most commonly applied to microtubules, but it also describes the pointed end of actin filaments. In microtubules, subunits are alpha-beta tubulin; the end with exposed alpha-tubulin typically constitutes the minus end, while the opposite end, with exposed beta-tubulin, is the plus end. The plus end is the primary site of rapid polymerization in many cells, whereas the minus end is generally more stable or capped.

In cells, minus ends are often anchored at microtubule organizing centers (MTOCs) such as centrosomes in animal cells or spindle pole bodies in yeasts. The gamma-tubulin ring complex nucleates microtubule assembly at MTOCs and remains associated with minus ends, helping anchor microtubules. Away from MTOCs, minus ends are protected by minus-end binding proteins (e.g., CAMSAP/Patronin families) that cap or stabilize them, reducing depolymerization.

Motor proteins: minus-end directed motors like cytoplasmic dynein move cargo toward the minus ends; plus-end-directed kinesins move toward the plus ends, organizing transport along microtubules.

In actin filaments: the minus end is known as the pointed end; it grows more slowly and is often stabilized by capping proteins such as tropomodulin, while the plus end is more dynamic.

Minus ends play key roles in establishing polarity and organization of cellular architecture, spindle dynamics during cell division, organelle positioning, and directed intracellular transport.