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Titolo:
Troponin organization on relaxed and activated thin filaments revealed by electron microscopy and three-dimensional reconstruction
Autore:
Lehman, W; Rosol, M; Tobacman, LS; Craig, R;
Indirizzi:
Boston Univ, Sch Med, Dept Physiol & Biophys, Boston, MA 02118 USA Boston Univ Boston MA USA 02118 t Physiol & Biophys, Boston, MA 02118 USA Univ Iowa, Coll Med, Dept Biochem, Iowa City, IA 52242 USA Univ Iowa IowaCity IA USA 52242 d, Dept Biochem, Iowa City, IA 52242 USA Univ Iowa, Coll Med, Dept Internal Med, Iowa City, IA 52242 USA Univ IowaIowa City IA USA 52242 pt Internal Med, Iowa City, IA 52242 USA Univ Massachusetts, Sch Med, Dept Cell Biol, Worcester, MA 01655 USA Univ Massachusetts Worcester MA USA 01655 l Biol, Worcester, MA 01655 USA
Titolo Testata:
JOURNAL OF MOLECULAR BIOLOGY
fascicolo: 3, volume: 307, anno: 2001,
pagine: 739 - 744
SICI:
0022-2836(20010330)307:3<739:TOORAA>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
3-DIMENSIONAL IMAGE-RECONSTRUCTION; INSECT FLIGHT-MUSCLE; TROPOMYOSIN; ACTIN; MODEL; BINDING; MYOSIN; LAYER;
Keywords:
actin; electron microscopy; muscle regulation; tropomyosin; troponin;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
34
Recensione:
Indirizzi per estratti:
Indirizzo: Lehman, W Boston Univ, Sch Med, Dept Physiol & Biophys, 715 Albany St, Boston, MA 02118 USA Boston Univ 715 Albany St Boston MA USA 02118 ston, MA 02118 USA
Citazione:
W. Lehman et al., "Troponin organization on relaxed and activated thin filaments revealed by electron microscopy and three-dimensional reconstruction", J MOL BIOL, 307(3), 2001, pp. 739-744

Abstract

The steric model of muscle regulation holds that at low Ca2+ concentration, tropomyosin strands, running along thin filaments, are constrained by troponin in an inhibitory position that blocks myosin-binding sites on actin. Ca2+ activation, releasing this constraint, allows tropomyosin movement, initiating actin-myosin interaction and contraction. Although the different positions of tropomyosin on the thin filament are well documented, corresponding information on troponin has been lacking and it has therefore not beenpossible to test the model structurally. Here, we show that troponin can be detected on thin filaments and demonstrate how its changing association with actin can control tropomyosin position in response to Ca2+ To accomplish this, thin filaments were reconstituted with an engineered short tropomyosin, creating a favorable troponin stoichiomtery and symmetry for three-dimensional analysis. We demonstrate that in the absence of Ca2+, troponin bound to both tropomyosin and actin can act as a latch to constrain tropomyosin in a position on actin that inhibits actomyosin ATPase. In addition, we find that on Ca2+ activation the actin-troponin connection is broken, allowing tropomyosin to assume a second position, initiating actomyosin ATPase and thus permitting contraction to proceed. (C) 2001 Academic Press.

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Documento generato il 19/01/20 alle ore 14:44:07