Tropomodulin binds two tropomyosins: a novel model for actin filament capping

Alla S Kostyukova; Andy Choy; Brian A Rapp

doi:10.1021/bi060899i

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Tropomodulin binds two tropomyosins: a novel model for actin filament capping

Journal article

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Tropomodulin binds two tropomyosins: a novel model for actin filament capping

Alla S Kostyukova, Andy Choy and Brian A Rapp

Biochemistry (Easton), Vol.45(39), pp.12068-12075

10/03/2006

DOI: https://doi.org/10.1021/bi060899i

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https://hdl.handle.net/2376/113771

PMCID: PMC2596622

PMID: 17002306

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Abstract

Amino Acid Sequence

Tropomyosin - genetics

Actin Cytoskeleton - metabolism

Protein Structure, Secondary

Humans

Molecular Sequence Data

Binding Sites - genetics

Tropomodulin - genetics

Cell Movement - physiology

Tropomodulin - metabolism

Muscle Contraction - physiology

Erythrocytes - metabolism

Protein Binding

Muscles - metabolism

Actin Cytoskeleton - genetics

Tropomyosin - metabolism

Tropomodulin, a tropomyosin-binding protein, caps the slow-growing (pointed) end of the actin filament regulating its dynamics. Tropomodulin, therefore, is important for determining cell morphology, cell movement, and muscle contraction. For the first time we show that one tropomodulin molecule simultaneously binds two tropomyosin molecules in a cooperative manner. On the basis of the tropomodulin solution structure and predicted secondary structure, we introduced a series of point mutations in regions important for tropomyosin binding and actin capping. Capping activity of these mutants was assayed by measuring actin polymerization using pyrene fluorescence. Using direct methods (circular dichroism and native gel electrophoresis) for detecting tropomodulin/tropomyosin binding, we localized the second tropomyosin-binding site to residues 109-144. Despite previous reports that the second binding site is for erythrocyte tropomyosin only, we found that both short nonmuscle and long muscle alpha-tropomyosins bind there as well, though with different affinities. We propose a model for actin capping where one tropomodulin molecule can bind to two tropomyosin molecules at the pointed end.

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Title: Tropomodulin binds two tropomyosins: a novel model for actin filament capping
Creators: Alla S Kostyukova - Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA. kostyuas@umdnj.edu
Andy Choy
Brian A Rapp
Publication Details: Biochemistry (Easton), Vol.45(39), pp.12068-12075
Academic Unit: Chemical Engineering and Bioengineering, School of
Publisher: United States
Grant note: R01 GM063257 / NIGMS NIH HHS GM63257 / NIGMS NIH HHS R01 GM063257-17 / NIGMS NIH HHS
Identifiers: 99900548377901842
Language: English
Resource Type: Journal article