minusänden

Minusänden, in Swedish "the minus end," refers to the end of a filament or polymer where subunits are added or removed in the direction opposite to the so-called plus end. The term is commonly used in discussions of cytoskeletal polymers such as microtubules and actin, where filament polarity underpins growth, shrinkage, and intracellular transport.

In microtubules, the minus end is typically anchored near the microtubule organizing center, such as the centrosome, while the plus end grows and shrinks more rapidly. The gamma-tubulin ring complex nucleates new microtubules and helps stabilize the minus ends, and specific proteins such as CAMSAPs contribute to minus-end stabilization. Motors that move toward the minus end, notably dynein, transport cargos in that direction. Minus ends can depolymerize under certain cellular conditions, influencing overall microtubule dynamics and organization.

In actin filaments, the minus end is known as the pointed end, and the plus end as the barbed end. Growth at the plus end is typically faster, while the minus end tends to depolymerize more slowly or be stabilized by proteins such as tropomodulin. Actin dynamics at the minus end are important for filament turnover and cellular processes like migration and shape changes; severing proteins and capping factors modulate both ends to regulate filament length and polarity.

Outside biology, the term describes the analogous end of other filamentous polymers where polarity affects assembly and interactions. The concept of a minus end highlights the directional nature of filament growth and cellular organization.