Key result
Tropomyosin molecules are proposed to diffuse over actin filaments to facilitate continuous, gap-free cable formation.
Why the study?
Little is known about the assembly process that leads to continuous, gap-free tropomyosin cable formation on actin thin filaments.
Key points are not available for this paper at this time.
Design
Other
Proposed tropomyosin diffusion on actin may enable gap-free cable assembly; leaves open relevance to cardiac thin-filament regulation.
Coiled-coil tropomyosin binds to consecutive actin-subunits along actin-containing thin filaments. Tropomyosin molecules then polymerize head-to-tail to form cables that wrap helically around the filaments. Little is known about the assembly process that leads to continuous, gap-free tropomyosin cable formation. We propose that tropomyosin molecules diffuse over the actin-filament surface to connect head-to-tail to partners. This possibility is likely because (1) tropomyosin hovers loosely over the actin-filament, thus binding weakly to F-actin and (2) low energy-barriers provide tropomyosin freedom for 1D axial translation on F-actin. We consider that these unique features of the actin-tropomyosin interaction are the basis of tropomyosin cable formation.
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Fischer et al. (2016) studied this question. Tropomyosin molecules are proposed to diffuse over the actin-filament surface to connect head-to-tail, facilitating continuous, gap-free cable formation.
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