Open AccessTropomyosin diffusion over actin subunits facilitates thin filament assembly
Author(s) -
Stefan Fischer,
Michael J. Rynkiewicz,
Jeffrey R. Moore,
William Lehman
Publication year - 2016
Publication title -
structural dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.415
H-Index - 29
ISSN - 2329-7778
DOI - 10.1063/1.4940223
Subject(s) - tropomyosin , protein filament , actin , coiled coil , actin remodeling , mdia1 , biophysics , actin binding protein , chemistry , microfilament , crystallography , actin cytoskeleton , biology , cytoskeleton , biochemistry , cell
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.