Treadmilling: key concept

In many cases the minus end of microtubules is capped (see later) so that growth and shrinkage of microtubules occurs only at the plus end. However in some circumstances (such as in mitosis) the minus end is free to undergo disassembly while the plus end is polymerising giving rise to the phenomenon known as treadmilling. In vitro this occurs when Cc (T)<C<Cc (D). When the rate of polymerisation at the plus end is equal to the rate of depolymerisation at the minus end the polymer stays the same length (as on the right) but microtubule flux occurs