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Zusammenfassung:
Cell cortex remodeling during cell division is a result of myofilament-driven
contractility of the cortical membrane-bound actin meshwork. Little is known about the
interaction between individual myofilaments and membrane-bound actin filaments. Here we
reconstituted a minimal actin cortex to directly visualize the action of individual myofilaments on
membrane-bound actin filaments using TIRF microscopy. We show that synthetic myofilaments
fragment and compact membrane-bound actin while processively moving along actin filaments.
We propose a mechanism by which tension builds up between the ends of myofilaments,
resulting in compressive stress exerted to single actin filaments, causing their buckling and
breakage. Modeling of this mechanism revealed that sufficient force (∼20 pN) can be generated
by single myofilaments to buckle and break actin filaments. This mechanism of filament
fragmentation and compaction may contribute to actin turnover and cortex reorganization during
cytokinesis.