Sandbox 154: Difference between revisions

Formation of F-actin is a dynamic process of assembly and disassembly which has been termed “treadmilling”.  

The transition between G- and F-actin begins with a stabilized oligomer of ATP-actin units formed through a nucleation-condensation type fold pattern<ref>pfaendtner</ref>. Addition of ATP-monomeric units to either end subsequently occurs, however, because of a difference in charge polarity in the two ends, there is preferential addition to what is termed the "plus (+) end" or the "barbed-end". On the opposite end, the "minus (-) end" or the "pointed end", there is preferential dissociation of actin units<ref>mitchinson</ref>. After attachment of the ATP-bound actin, hydrolysis of the ATP occurs yielding the ADP+Pi bound state. Subsequent loss of a Pi leaves the ADP-actin state<ref>chen</ref>. Because of the potential for addition or removal of monomeric units to occur at both ends, the assembly of F-actin may be described in terms of equilibrium. However, because the rate of ATP-actin association is ten-fold that of ADP-actin dissociation, the f-actin has the appearance of moving forward, or "treadmilling"<ref>clasier</ref>. ADP-actin monomers dissociate at the minus end and become recycled to ATP-actin so polymerization at the plus end may occur once again.

== Structure ==