The mobility of troponin C and troponin I in muscle

Li, Hui Chun; Hideg, Kálmán; Fajer, Piotr G.

doi:10.1002/(sici)1099-1352(199707/08)10:4<194::aid-jmr365>3.0.co;2-x

Cited by 11 publications

(9 citation statements)

References 32 publications

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“…Conventional EPR spectra of randomly oriented samples (myofibrils) and saturation transfer EPR experiments showed that the spin label is immobilized on the nanosecond time scale of the experiments presented below and on the millisecond time scale of the ST-EPR experiments (11,24). Thus the spectral changes which we report below are due to changes in the orientational distribution of the labeled domain at Cys98 of TnC and not due to motion of the label with respect to the protein.…”

Section: Resultssupporting

confidence: 85%

Structural Coupling of Troponin C and Actomyosin in Muscle Fibers

Fajer

1998

Biochemistry

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EPR of spin labeled TnC at Cys98 was used to explore the possible structural coupling between TnC in the thin filament and myosin trapped in the intermediate states of ATPase cycle. Weakly attached myosin heads (trapped by low ionic strength, low temperature and ATP) did not induce structural changes in TnC as compared to relaxed muscle, as spin labeled TnC displayed the same narrow orientational distribution [Li, H.-C., and Fajer, P. G. (1994) Biochemistry 33, 14324]. Ca2+-binding alone resulted in disordering of the labeled domain of TnC. Additional conformational changes of TnC occurred upon the attachment of strongly bound, prepower stroke myosin heads (trapped by AlF4-). These changes were not present in ghost fibers which myosin had been removed, excluding direct effects of AlF4- on the orientation of TnC in muscle fibers. The postpower stroke heads (rigor.ADP/Ca2+ and rigor/Ca2+) induced further changes in the orientational distribution of labeled domain of TnC irrespective of the degree of cooperativity in thin filaments. We thus conclude that troponin C in thin filaments detects structural changes in myosin during force generation, implying that there is a structural coupling between actomyosin and TnC.

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Section: Resultssupporting

confidence: 85%

Structural Coupling of Troponin C and Actomyosin in Muscle Fibers

Fajer

1998

Biochemistry

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“…[20][21][22][23] Although in vitro structures are available for most of the troponin components and their complexes, obtained by X-ray, NMR and FRET methods, it is important to observe dynamic interactions in the complexes in situ. Electron paramagnetic resonance (EPR) is a powerful tool for measuring the mobility of spin labels attached to a domain in a protein, [24][25][26][27][28][29][30] by determining the angle of spin label toward a magnetic field [31][32][33][34][35] and the distance between two spin labels. 36,37 The methods for exchange of TnC and myosin light chain in muscle fibres [38][39][40] have made it possible to follow the conformational changes of TnC or myosin neck in permeabilized muscle fibre systems.…”

Section: Introductionmentioning

confidence: 99%

Calcium Structural Transition of Human Cardiac Troponin C in Reconstituted Muscle Fibres as Studied by Site-directed Spin Labelling

Nakamura

Ueki

Hara³

et al. 2005

Journal of Molecular Biology

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“…InVSL has been previously found to be fully immobilized on a number of proteins, e.g., skeletal myosin S1 and ELC (27,28), RLC (29), troponin C and troponin I (41). To check the immobilization of InVSL on Cys-108 of gRLC we have cross-linked the InVSL-RLC to DITC-coated glass beads.…”

Section: Invsl As a Probe For Domain Motionmentioning

confidence: 57%

Regulatory and Catalytic Domain Dynamics of Smooth Muscle Myosin Filaments

Song

Salzameda

et al. 2006

Biochemistry

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Domain dynamics of the chicken gizzard smooth muscle myosin catalytic domain (heavy chain Cys-717) and regulatory domain (regulatory light chain Cys-108) were determined in the absence of nucleotides using saturation-transfer electron paramagnetic resonance. In unphosphorylated synthetic filaments, the effective rotational correlation times, τ r , were 24 ± 6 μs and 441 ± 79 μs for the catalytic and regulatory domains, respectively. The corresponding amplitudes of motion were 42 ± 4° and 24 ± 9° as determined from steady-state phosphorescence anisotropy. These results suggest that the two domains have independent mobility due to a hinge between the two domains. Although a similar hinge was observed for skeletal myosin (Adhikari and Fajer (1997) Proc. Natl. Acad. Sci. U.S. A. 94, 9643-9647. Brown et al. (2001) Biochemistry 40,[8283][8284][8285][8286][8287][8288][8289][8290][8291], the latter displayed higher regulatory domain mobility, τ r = 40 ± 3 μs, suggesting a smooth muscle specific mechanism of constraining regulatory domain dynamics. In the myosin monomers the correlation times for both domains were the same (~4 μs) for both smooth and skeletal myosin, suggesting that the motional difference between the two isoforms in the filaments was not due to intrinsic variation of hinge stiffness. Heavy chain/regulatory light chain chimeras of smooth and skeletal myosin pinpointed the origin of the restriction to the heavy chain and established correlation between the regulatory domain dynamics with the ability of myosin to switch off but not to switch on the ATPase and the actin sliding velocity. Phosphorylation of smooth muscle myosin filaments caused a small increase in the amplitude of motion of the regulatory domain (from 24 ± 4° to 36 ± 7°) but did not significantly affect the rotational correlation time of the regulatory domain (441 to 408 μs) or the catalytic domain (24 to 17 μs). These data are not consistent with a stable interaction between the two catalytic domains in unphosphorylated smooth muscle myosin filaments in the absence of nucleotides. † This material is based upon work supported by the National Science Foundation under Grant No. 0346650, the AHA GIA 0455236B to P.G.F., and NIH AR40917 to C.R.C. and TCMRC 90103 to H.-C.L. L.S. is a recipient of American Heart Graduate Fellowship. *Author to whom correspondence should be addressed. Mailing address: Inst. Molecular Biophysics, Florida State University, Tallahassee, FL 32306. Tel: 850-645-1335. Fax: 850-644-1366. fajer@magnet.fsu.edu. ‡ Florida State University. § Tzu-Chi University. || These authors contributed equally. ⊥ University of Nevada School of Medicine. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptMyosins are a superfamily of motor proteins that convert the chemical energy derived from ATP hydrolysis to mechanical energy by generating movement or force. Myosin II, the major protein from muscle, consists of two globular head domains and a coiled-coil tail or rod domain. At physiological...

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The mobility of troponin C and troponin I in muscle

Cited by 11 publications

References 32 publications

Structural Coupling of Troponin C and Actomyosin in Muscle Fibers

Structural Coupling of Troponin C and Actomyosin in Muscle Fibers

Calcium Structural Transition of Human Cardiac Troponin C in Reconstituted Muscle Fibres as Studied by Site-directed Spin Labelling

Regulatory and Catalytic Domain Dynamics of Smooth Muscle Myosin Filaments

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