Premium
Pointed‐end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers
Author(s) -
Ochala Julien,
Gokhin David S.,
Iwamoto Hiroyuki,
Fowler Velia M.
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.13-239640
Subject(s) - crossbridge , tropomyosin , actin , skeletal muscle , biophysics , contractility , protein filament , myofibril , myosin , myofilament , muscle contraction , nebulin , chemistry , crystallography , anatomy , microbiology and biotechnology , biology , sarcomere , biochemistry , myocyte , titin , endocrinology
In skeletal muscle, thick and thin filaments are arranged in a myofibrillar lattice. Tropomodulin 1 (Tmod1) is a pointed‐end capping and tropomyosin‐binding protein that controls thin‐filament assembly, stability, and lengths. It remains unknown whether Tmods have other functional roles, such as regulating muscle contractility. To investigate this, we recorded and analyzed the mechanical properties and X‐ray diffraction patterns of single membrane‐permeabilized skeletal muscle fibers from mice lacking Tmod1. Results show that absence of Tmod1 and its replacement by Tmod3 and Tmod4 may impair initial tropomyosin movement over actin subunits during thin‐filament activation, thus reducing both the fraction of actomyosin crossbridges in the strongly bound state (–29%) and fiber force‐generating capacity (–31%). Therefore, Tmods are novel regulators of actomyosin crossbridge formation and muscle contractility, and future investigations and models of skeletal muscle force production must incorporate Tmods.—Ochala, J., Gokhin, D. S., Iwamoto, H., Fowler, V. M. Pointed‐end capping by tropomodulin modulates actomyosin crossbridge formation in skeletal muscle fibers. FASEB J . 28, 408–415 (2014). www.fasebj.org