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Tropomyosin is a tetramer under physiological salt conditions
Author(s) -
Lassing Ingrid,
Hillberg Louise,
Höglund AnnaStina,
Karlsson Roger,
Schutt Clarence,
Lindberg Uno
Publication year - 2010
Publication title -
cytoskeleton
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 86
eISSN - 1949-3592
pISSN - 1949-3584
DOI - 10.1002/cm.20470
Subject(s) - tropomyosin , tetramer , actin , myosin , biophysics , stokes radius , biology , skeletal muscle , coiled coil , ultracentrifuge , depolymerization , microfilament , dimer , biochemistry , size exclusion chromatography , cytoskeleton , anatomy , chemistry , cell , enzyme , organic chemistry
Tropomyosin (TM) is a coiled‐coil dimer of α‐helical peptides, which self associates in a head‐ to‐tail fashion along actin polymers, conferring stability to the microfilaments and serving a regulatory function in acto‐myosin driven force generation. While the major amount of TM is associated with filaments also in non‐muscle cells, it was recently reported that there are isoform‐specific pools of TM multimers (not associated with F‐actin), which appear to be utilized during actin polymerization and reformed during depolymerization. To determine the size of these multimers, skeletal muscle TM was studied under different salt conditions using gel‐filtration and sucrose gradient sedimentation, and compared with purified non‐muscle TM 1 and 5, as well as with TM present in non‐muscle cell extracts and skeletal muscle TM added to such extracts. Under physiological salt conditions TM appears as a single homogenous peak with the Stokes radius 8.2 nm and the molecular weight (mw) 130,000. The corresponding values for TM 5 are 7.7 nm and 104,000, respectively. This equals four peptides, implying that native TM is a tetramer in physiological salt. It is therefore concluded that the TM multimers are tetramers. © 2010 Wiley‐Liss, Inc.