Non‐polymerizability of platelet tropomyosin and its NH<sub>2</sub>‐ and COOH‐terminal sequences

Côté, Graham P.; Lewis, William; Smillie, Lawrence B.

doi:10.1016/0014-5793(78)81181-8

Cited by 59 publications

(1 citation statement)

References 31 publications

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“…The structural differences among the isoforms, especially at the N-terminus (Greenfield et al 1998; Greenfield et al 2001), give the isoforms divergent functional properties such as actin-binding affinities (Mak et al 1987; Novy et al 1993; Fanning et al 1994; Moraczewska et al 1999), inclination for head-to-tail association (Cote et al 1978; Dabrowska et al 1983) and Tmod-binding affinities (Greenfield and Fowler 2002; Uversky et al 2011). Different TM isoforms are responsible for the regulation of cell motility and the organization of actin filaments in various cell types.…”

Section: Tropomyosinmentioning

confidence: 99%

Tropomodulins and tropomyosins: working as a team

Colpan

Moroz

Kostyukova

2013

J Muscle Res Cell Motil

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Actin filaments are major components of the cytoskeleton in eukaryotic cells and are involved in vital cellular functions such as cell motility and muscle contraction. Tropomyosin is an alpha-helical, coiled coil protein that covers the grooves of actin filaments and stabilizes them. Actin filament length is optimized by tropomodulin, which caps the slow growing (pointed end) of thin filaments to inhibit polymerization or depolymerization. Tropomodulin consists of two structurally distinct regions: the N-terminal and the C-terminal domains. The N-terminal domain contains two tropomyosin-binding sites and one tropomyosin-dependent actin-binding site, whereas the C-terminal domain contains a tropomyosin-independent actin-binding site. Tropomodulin binds to two tropomyosin molecules and at least one actin molecule during capping. The interaction of tropomodulin with tropomyosin is a key regulatory factor for actin filament organization. The binding efficacy of tropomodulin to tropomyosin is isoform-dependent. The affinities of tropomodulin/tropomyosin binding influence the proper localization and capping efficiency of tropomodulin at the pointed end of actin filaments in cells. Tropomodulin and tropomyosin are crucial constituents of the actin filament network, making their presence indispensable in living cells. Here we describe how a small difference in the sequence of the tropomyosin-binding sites of tropomodulin may result in dramatic change in localization of Tmod in muscle cells or morphology of non-muscle cells. We also suggest most promising directions to study and elucidate the role of Tmod-TM interaction in formation and maintenance of sarcomeric and cytoskeletal structure.

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Section: Tropomyosinmentioning

confidence: 99%

Tropomodulins and tropomyosins: working as a team

Colpan

Moroz

Kostyukova

2013

J Muscle Res Cell Motil

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Tropomyosin is a tetramer under physiological salt conditions

et al. 2010

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Tropomyosin (TM) is a coiled-coil dimer of alpha-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.

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Tropomyosin binding to F‐actin protects the F‐actin from disassembly by brain actin‐depolymerizing factor (ADF)

1982

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Brain or muscle F-actin is rapidly depolymerized to monomeric actin in vitro by actin-depolymerizing factor, a protein isolated from chick embryo brain. Binding of muscle tropomyosin to muscle F-actin protects the F-actin from depolymerization by this factor. A 8.4/1.0 molar ratio of actin subunits to tropomyosin, achieved by incubation of the F-actin with excess tropomyosin, protects 58% of the F-actin from depolymerization by excess actin-depolymerizing factor for at least 3 hr at 25 degrees C. Thus, actin-depolymerizing factor seems to be specifically directed toward actin filaments lacking tropomyosin.

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Non‐polymerizability of platelet tropomyosin and its NH₂‐ and COOH‐terminal sequences

Cited by 59 publications

References 31 publications

Tropomodulins and tropomyosins: working as a team

Tropomodulins and tropomyosins: working as a team

Tropomyosin is a tetramer under physiological salt conditions

Tropomyosin binding to F‐actin protects the F‐actin from disassembly by brain actin‐depolymerizing factor (ADF)

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Non‐polymerizability of platelet tropomyosin and its NH2‐ and COOH‐terminal sequences

Cited by 59 publications

References 31 publications

Tropomodulins and tropomyosins: working as a team

Tropomodulins and tropomyosins: working as a team

Tropomyosin is a tetramer under physiological salt conditions

Tropomyosin binding to F‐actin protects the F‐actin from disassembly by brain actin‐depolymerizing factor (ADF)

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Non‐polymerizability of platelet tropomyosin and its NH₂‐ and COOH‐terminal sequences