Editing Microfilament (section)

===Steps involved===
The following steps describe one force-generating cycle of an actoclampin molecular motor:
# The polymerization cofactor profilin and the ATP·actin combine to form a profilin-ATP-actin complex that then binds to the end-tracking unit
# The cofactor and monomer are transferred to the barbed-end of an actin already clamped filament
# The tracking unit and cofactor dissociate from the adjacent protofilament, in a step that can be facilitated by ATP hydrolysis energy to modulate the affinity of the cofactor and/or the tracking unit for the filament; and this mechanoenzymatic cycle is then repeated, starting this time on the other sub-filament growth site.{{cn|date=January 2023}}

When operating with the benefit of ATP hydrolysis, AC motors generate per-filament forces of 8–9 pN, which is far greater than the per-filament limit of 1–2 pN for motors operating without ATP hydrolysis.<ref name=D&P2002/><ref name=DCP2004/><ref>{{Cite journal |vauthors=Dickinson RB, Purich DL |date=August 2006 |title=Diffusion rate limitations in actin-based propulsion of hard and deformable particles |journal=Biophysical Journal |volume=91 |issue=4 |pages=1548–63 |bibcode=2006BpJ....91.1548D |doi=10.1529/biophysj.106.082362 |pmc=1518650 |pmid=16731556}}</ref>  The term actoclampin is generic and applies to all actin filament end-tracking molecular motors, irrespective of whether they are driven actively by an ATP-activated mechanism or passively.{{cn|date=December 2024}}

Some actoclampins (e.g., those involving Ena/VASP proteins, WASP, and N-WASP) apparently require Arp2/3-mediated filament initiation to form the [[actin polymerization]] nucleus that is then "loaded" onto the end-tracker before processive motility can commence. To generate a new filament, Arp2/3 requires a "mother" filament, monomeric ATP-actin, and an activating domain from Listeria ActA or the VCA region of N-WASP. The Arp2/3 complex binds to the side of the mother filament, forming a Y-shaped branch having a 70-degree angle with respect to the [[Anatomical terms of location|longitudinal]] axis of the mother filament. Then upon activation by ActA or VCA, the Arp complex is believed to undergo a major conformational change, bringing its two actin-related protein subunits near enough to each other to generate a new filament gate. Whether ATP hydrolysis may be required for nucleation and/or Y-branch release is a matter under active investigation.{{cn|date=December 2024}}