Changes in Actin and Myosin Structural Dynamics Due to Their Weak and Strong Interactions

Thomas, David D.; Próchniewicz, Ewa; Roopnarine, Osha

doi:10.1007/978-3-540-46558-4_2

Cited by 28 publications

(36 citation statements)

References 51 publications

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“…The actin rotational dynamics involves multiple modes and time scales (Fig. 4) (13): intraprotomer motions on the submicrosecond time scale, intrafilament torsional motions on the microsecond time scale, and filament bending motions on both microsecond and millisecond time scales (23). Our results indicate that utrophin affects all of these modes more profoundly than does dystrophin.…”

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confidence: 74%

Dystrophin and utrophin have distinct effects on the structural dynamics of actin

Próchniewicz

Henderson

Ervasti

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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We have used time-resolved spectroscopy to investigate the structural dynamics of actin interaction with dystrophin and utrophin in relationship to the pathology of muscular dystrophy. Dystrophin and utrophin bind actin in vitro with similar affinities, but the molecular contacts of these two proteins with actin are different. It has been hypothesized that the presence of two low-affinity actin-binding sites in dystrophin allows more elastic response of the actin-dystrophin-sarcolemma linkage to muscle stretches, compared with utrophin, which binds via one contiguous actinbinding domain. We have directly tested this hypothesis by determining the effects of dystrophin and utrophin on the microsecond rotational dynamics of a phosphorescent dye attached to C374 on actin, as detected by transient phosphorescence anisotropy (TPA). Binding of dystrophin or utrophin to actin resulted in significant changes in the TPA decay, increasing the final anisotropy (restricting the rotational amplitude) and decreasing the rotational correlation times (increasing the rotational rates and the torsional flexibility). This paradoxical combination of effects on actin dynamics (decreased amplitude but increased rate) has not been observed for other actin-binding proteins. Thus, when dystrophin or utrophin binds, actin becomes less like cast iron (strong but brittle) and more like steel (stronger and more resilient). At low levels of saturation, the binding of dystrophin and utrophin has similar effects, but at higher levels, utrophin caused much greater restrictions in amplitude and increases in rate. The effects of dystrophin and utrophin on actin dynamics provide molecular insight into the pathology of muscular dystrophy. muscular dystrophy ͉ spectroscopy ͉ flexibility ͉ phosphorescence

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confidence: 74%

Dystrophin and utrophin have distinct effects on the structural dynamics of actin

Próchniewicz

Henderson

Ervasti

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…2 This step is postulated to follow cTnI-R association with a hydrophobic patch on Ca 2þ -bound N-TnC. 3 These changes, together with the lateral movement of Tm on the thin filament, 4 and changes in filamentous actin (A 7 ) structure and dynamics, 5 activate the thin filament (TnTmA 7 ), permitting actin-myosin cross-bridge cycling and force development.…”

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confidence: 99%

Switching of Troponin I: Ca2+ and Myosin-induced Activation of Heart Muscle

Robinson

Dong

Xing

et al. 2004

Journal of Molecular Biology

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“…Bundled within an intricate and highly regulated myofibril lattice, muscle myosin II converts the chemical energy released by ATP binding and hydrolysis into mechanical work, executing a series of structural transitions that generate force on actin and shorten each muscle cell (1,2). Coupling of actin binding, nucleotide hydrolysis, and lever arm movement within myosin's catalytic domain (CD) is essential for proper function of the contractile apparatus (3,4).…”

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High-resolution helix orientation in actin-bound myosin determined with a bifunctional spin label

Binder

Cornea

Thompson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Using electron paramagnetic resonance (EPR) of a bifunctional spin label (BSL) bound stereospecifically to Dictyostelium myosin II, we determined with high resolution the orientation of individual structural elements in the catalytic domain while myosin is in complex with actin. BSL was attached to a pair of engineered cysteine side chains four residues apart on known α-helical segments, within a construct of the myosin catalytic domain that lacks other reactive cysteines. EPR spectra of BSL-myosin bound to actin in oriented muscle fibers showed sharp three-line spectra, indicating a well-defined orientation relative to the actin filament axis. Spectral analysis indicated that orientation of the spin label can be determined within <2.1°accuracy, and comparison with existing structural data in the absence of nucleotide indicates that helix orientation can also be determined with <4.2°accuracy. We used this approach to examine the crucial ADP release step in myosin's catalytic cycle and detected reversible rotations of two helices in actin-bound myosin in response to ADP binding and dissociation. One of these rotations has not been observed in myosin-only crystal structures.T he myosin family of molecular motors is responsible for numerous vital functions in eukaryotes, including the contraction of striated muscle. Bundled within an intricate and highly regulated myofibril lattice, muscle myosin II converts the chemical energy released by ATP binding and hydrolysis into mechanical work, executing a series of structural transitions that generate force on actin and shorten each muscle cell (1, 2). Coupling of actin binding, nucleotide hydrolysis, and lever arm movement within myosin's catalytic domain (CD) is essential for proper function of the contractile apparatus (3, 4).Myosin function requires actin, and thus an understanding of its mechanism requires analysis of both proteins in complex. However, no crystals of actin-myosin complexes have been reported, so the resolution of actin-bound myosin structures is currently limited to that of electron microscopy. Furthermore, X-ray crystallography and electron microscopy produce only static structures in frozen or crystalline environments, which cannot accurately render the dynamics, disorder, and structural transitions that are essential to understanding function and pathology (4, 5).In contrast, site-directed spectroscopy can be used to examine the actin-myosin complex under more physiological conditions. Both fluorescence and electron paramagnetic resonance (EPR) have been used in complement to examine the structural dynamics of myosin bound to actin (6, 7). EPR offers superior orientational resolution, due to the high sensitivity of the EPR spectrum to alignment of a spin label in the applied magnetic field. A wellplaced spin label can provide direct information about orientation and dynamics in the vicinity of the labeling site, a strategy that has proven powerful in the study of myosin in oriented muscle fibers (7-9). However, conventional methods for site-direc...

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Changes in Actin and Myosin Structural Dynamics Due to Their Weak and Strong Interactions

Cited by 28 publications

References 51 publications

Dystrophin and utrophin have distinct effects on the structural dynamics of actin

Dystrophin and utrophin have distinct effects on the structural dynamics of actin

Switching of Troponin I: Ca2+ and Myosin-induced Activation of Heart Muscle

High-resolution helix orientation in actin-bound myosin determined with a bifunctional spin label

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