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Actin has the ability to hydrolyze its bound with ATP to ADP + Pi , parting away Pi . The actin monomer can share bound ADP to ATP. The conformation of actin is change, relying on whether there is ADP or ATP in the nucleotide binding site or not.

G-actin known as globular actin with bound ATP has the tendency of tp polymerize and form F-actin grossly known as filamentous actin.
F-actin might hydrolyze its bound ATP to ADP + Pi which results in Pi. Thereby, ADP released from filament. Since the cleft is blocked it does not occur.

ATP/ADP exchange: G-actin could expel ADP and binding ATP, which is undoubtedly available in the cytosol with higher concentration than ADP.
Actin filaments are full with polarity. The actin monomers are aligned to their cleft towards the same end of the filament (designated the minus end). Actin monomers spiral exist around the axis of the filament, with a simple structure matching a double helix.

The polarity of actin filaments can be seen by decorating the filaments with globular heads (designated S1) cleaved off myosin by proteases.
In an experiment, short actin filaments had been decorated under myosin heads. After exclusion of excess unbound myosin, the concentration of G-actin had augmented to engulf more actin polymerization.
On the one hand filement had growth with positive (+) and on the other hand it had a negative growth (-).

Actin filaments might go through the treadmilling in which process filament length remains approximately same, but actin monomers add plus end and dissociate from the minus end. This had been monitored by using concise exposure to label actin monomers called as pulse labeling.

Besides, there are captin proteins which have the ability to determine the exact filament length. Tropomodulins prevent disunification of monomers at the minus end. On the other hand, capping protein binds with the positive end causing augmentation of polymerization.