Journal article
The Role of Tropomyosin Domains in Cooperative Activation of the Actin–Myosin Interaction
Journal of molecular biology, Vol.414(5), pp.667-680
12/16/2011
DOI: 10.1016/j.jmb.2011.10.026
PMCID: PMC3230701
PMID: 22041451
Abstract
To establish α-tropomyosin (Tm)'s structure–function relationships in cooperative regulation of muscle contraction, thin filaments were reconstituted with a variety of Tm mutants (Δ2Tm, Δ3Tm, Δ6Tm, P2sTm, P3sTm, P2P3sTm, P1P5Tm, and wtTm), and force and sliding velocity of the thin filament were studied using an in vitro motility assay. In the case of deletion mutants, Δ indicates which of the quasi-equivalent repeats in Tm was deleted. In the case of period (P) mutants, an Ala cluster was introduced into the indicated period to strengthen the Tm–actin interaction. In P1P5Tm, the N-terminal half of period 5 was substituted with that of period 1 to test the quasi-equivalence of these two Tm periods. The reconstitution included bovine cardiac troponin. Deletion studies revealed that period 3 is important for the positive cooperative effect of Tm on actin filament regulation and that period 2 also contributes to this effect at low ionic strength, but to a lesser degree. Furthermore, Tm with one extra Ala cluster at period 2 (P2s) or period 3 (P3s) did not increase force or velocity, whereas Tm with two extra Ala clusters (P2P3s) increased both force and velocity, demonstrating interaction between these periods. Most mutants did not move in the absence of Ca2+. Notable exceptions were Δ6Tm and P1P5Tm, which moved near at the full velocity, but with reduced force, which indicate impaired relaxation. These results are consistent with the mechanism that the Tm–actin interaction cooperatively affects actin to result in generation of greater force and velocity.
► The structure–function relationship of α-Tm was investigated. ► Deletion (Δ) and shift mutants of Tm were used with in vitro motility assays. ► Significance of Tm's period 3 was demonstrated for cooperative activation of actin. ► A large increase in cooperativity when Ala cluster was introduced to periods 2 and 3. ► Δ6Tm impaired relaxation because of uncoupling of C-TnT/TnIReg with period 5.
Details
- Title: Subtitle
- The Role of Tropomyosin Domains in Cooperative Activation of the Actin–Myosin Interaction
- Creators
- Yusuke Oguchi - 1Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, JapanJunji Ishizuka - 1Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, JapanSarah E Hitchcock-DeGregori - Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Piscataway, NJ 08554, USAShin'ichi Ishiwata - 1Department of Physics, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, JapanMasataka Kawai - 3Department of Anatomy and Cell Biology, College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Resource Type
- Journal article
- Publication Details
- Journal of molecular biology, Vol.414(5), pp.667-680
- DOI
- 10.1016/j.jmb.2011.10.026
- PMID
- 22041451
- PMCID
- PMC3230701
- NLM abbreviation
- J Mol Biol
- ISSN
- 0022-2836
- eISSN
- 1089-8638
- Publisher
- Elsevier Ltd
- Grant note
- name: Grants-in-Aid for Specially Promoted Research and Scientific Research (S) from the Ministry of Education, Sports, Culture, Science and Technology of Japan to S.I.; DOI: 10.13039/100000002, name: National Institutes of Health, award: GM36326, GM93065; name: University of Medicine and Dentistry of New Jersey Foundation to S.E.H.D.; DOI: 10.13039/100000002, name: National Institutes of Health, award: HL70041; DOI: 10.13039/100000968, name: American Heart Association, award: 0850184Z
- Language
- English
- Date published
- 12/16/2011
- Academic Unit
- Anatomy and Cell Biology; Internal Medicine
- Record Identifier
- 9984025425402771
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