Atomic Structure of Scallop Myosin Subfragment S1 Complexed with MgADP

Houdusse, Anne; Kalabokis, Vassilios N.; Himmel, D.M.; Szent‐Györgyi, Albert; Cohen, Carolyn

doi:10.1016/s0092-8674(00)80756-4

Cited by 337 publications

(358 citation statements)

References 36 publications

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“…More detailed understanding of the molecular basis of force generation came with the description of the S1 (the head portion of the myosin molecule) subfragment on the atomic level (Houdusse et al, 1999) in the absence of nucleotide and in the presence of various nucleotides and analogs (MgADP, AMPPNP, ADP°BeF x ) that induce different myosin head conformations (Houdusse et al, 2000;Himmel et al, 2002;Gourinath et al, 2003;Nitao et al, 2003;Risal et al, 2004). This work has identified the converter and lever arm domains of the molecule (Houdusse et al, 1999), shown that the heads can exist in a large number of different conformations as a result of rearrangements of the four domains of the head around three joints (Houdusse et al, 1999(Houdusse et al, , 2000Himmel et al, 2002;Gourinath et al, 2003), identified a hinge within the regulatory light chain domain of the lever arm that may be an important component of cross-bridge compliance (Gourinath et al, 2003), shown that the so-called SH1 helix may unwind to function as a clutch between the converter and lever arms (Himmel et al, 2002;Gourinath et al, 2003), shown that differences in the SH1 helix underlie some speciesspecific differences in myosin function (Nitao et al, 2003), been used in model search protocols to identify the lowest energy actin binding configurations of the head (Root, 2002a), and shown that the energy released by ATP hydrolysis spreads throughout the head and induces collective changes in the structure of the myosin neck and actin binding regions (Kawakubo et al, 2005).…”

Section: 32mentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

131

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This is the second in a series of canonical reviews on invertebrate muscle. We cover here thin and thick filament structure, the molecular basis of force generation and its regulation, and two special properties of some invertebrate muscle, catch and asynchronous muscle. Invertebrate thin filaments resemble vertebrate thin filaments, although helix structure and tropomyosin arrangement show small differences. Invertebrate thick filaments, alternatively, are very different from vertebrate striated thick filaments and show great variation within invertebrates. Part of this diversity stems from variation in paramyosin content, which is greatly increased in very large diameter invertebrate thick filaments. Other of it arises from relatively small changes in filament backbone structure, which results in filaments with grossly similar myosin head placements (rotating crowns of heads every 14.5 nm) but large changes in detail (distances between heads in azimuthal registration varying from three to thousands of crowns). The lever arm basis of force generation is common to both vetebrates and invertebrates, and in some invertebrates this process is understood on the near atomic level. Invertebrate actomyosin is both thin (tropomyosin:troponin) and thick (primarily via direct Ca ++ binding to myosin) filament regulated, and most invertebrate muscles are dually regulated. These mechanisms are well understood on the molecular level, but the behavioral utility of dual regulation is less so. The phosphorylation state of the thick filament associated giant protein, twitchin, has been recently shown to be the molecular basis of catch. The molecular basis of the stretch activation underlying asynchronous muscle activity, however, remains unresolved.

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Section: 32mentioning

confidence: 99%

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Hooper

Hobbs

Thuma

2008

Progress in Neurobiology

131

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“…The C-terminal lobe, which contains helices E-H forms more bonds with the long target helix of the myosin heavy chain than does the N-terminal lobe [2]. It is also located adjacent to the myosin motor domain [3] and differences in the interaction between the C-terminal lobe of the ELC and the motor domain in myosins of various origins may result in differences in the bending of the heavy chain helix and therefore in different orientations of the lever arm [43]. Therefore, helices E and H on the one hand, and helices F and G on the other hand may act as pairs of pincers to hold the myosin heavy chain.…”

Section: Discussionmentioning

confidence: 99%

Functional regions in the essential light chain of smooth muscle myosin as revealed by the mutagenesis approach

Quevillon‐Chéruel

Janmot

Nozais

et al. 2000

European Journal of Biochemistry

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The endogenous essential light chain (LC17) of myosin from intestine smooth muscle was replaced with mutated essential light chains prepared using recombinant techniques. Complete exchange was observed with histidinetagged derivatives of LC17a, LC17b and E122A-LC17a (LC17a and LC17b are the usual constituants of smooth muscle myosin), with small changes in the ATPase activity of reconstituted myosins. Much less exchange was observed with the light-chain derivative lacking the last 12 amino acid residues, demonstrating the importance of this segment, which may act as one arm of a pair of pincers to bind the myosin heavy chain.Keywords: isoforms; mutants; myosin light chains; site-directed mutagenesis; smooth muscle.Myosin II is a major contractile protein composed of two heavy chains (< 200 kDa each) and two pairs of light chains (< 20 kDa each). One pair of light chains is described as regulatory (20 kDa) and the other as essential (17 kDa), based on their distinctive chemical and functional features. In smooth muscle myosin, the two 20-kDa regulatory chains (LC20) can be phosphorylated and phosphorylation generates high levels of actin-activated ATPase activity and actin motility. The other pair of myosin light chains consists of the two 17-kDa essential chains (LC17), the functional significance of which is unclear [1]. The regulatory and essential light chains are bound to an 8-nm stretch of myosin heavy chain, mostly a helix. This complex constitutes a regulatory domain [2,3] and is thought to act as a lever arm during force production by muscle motor proteins [4].The essential light chain, LC17, has two isoforms, the ratio of which depends on the tissue. The difference between these two species is five amino acid substitutions in the nine C-terminal residues (Fig. 1). In particular, one isoform, LC17a, has a charged glutamic acid residue at position 142, whereas the other, LC17b, has an alanine residue in the corresponding position [5]. An inverse correlation has been found between relative LC17b content and the maximal shortening velocity of skinned smooth muscle fibers [6] but this result is controversial [1]. Recently, weak but significant LC17 isoform-specific effects on the mechanical properties of smooth muscle cells [7] and strips [8] have been shown. In addition, the two isoforms have different subcellular distributions suggesting that they may have different functions [9].It has been shown that substitution mutations in the essential light chain of nonmuscle myosin from Dictyostelium may lead to decreases in actin-activated ATPase activity and motor function, as assessed by an in vitro motility assay [10].Katoh and co-workers [11,12] recently reported an efficient method for essential light chain exchange in smooth muscle myosin. We used this method to exchange LC17a, LC17b and mutated essential light chains with endogenous light chains from rabbit small-intestine myosin. The recombinant proteins were prepared ( Fig. 1; ELC1±6) with a histidine tag on their N-terminus to facilitate purification. In...

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“…Analysis of the binding site is complicated because several of the surface loops on the S1 model are undefined [40,41,35] and that models for F-actin are still undergoing refinement. The binding affinity of myosin and actin varies with the chemical state of the bound nucleotide.…”

Section: Actomyosin Interfacementioning

confidence: 99%

“…[41]. These states are differentiated depending on the substructure of the 50kDa cleft, the converter region, and the position of the lever arm.…”

Section: Conformational Studies Of Myosin S1mentioning

confidence: 99%

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Fluorescence labeling and computational analysis of the strut of myosin’s 50 kDa cleft

Gawalapu¹,

Root²

2006

Archives of Biochemistry and Biophysics

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Gawalapu, Ravi Kumar. Fluorescence labeling and computational analysis of the strut of myosin's 50 kDa cleft. Doctor of Philosophy (Biochemistry), August 2007, 148 pp., 3 tables, 60 illustrations, 120 references, 120 titles.In order to understand the structural changes in myosin S1, fluorescence polarization and computational dynamics simulations were used. Dynamics simulations on the S1 motor domain indicated that significant flexibility was present throughout the molecular model. The constrained opening versus closing of the 50 kDa cleft appeared to induce opposite directions of movement in the lever arm. A sequence called the "strut" which traverses the 50 kDa cleft and may play an important role in positioning the actomyosin binding interface during actin binding is thought to be intimately linked to distant structural changes in the myosin's nucleotide cleft and neck regions. To study the dynamics of the strut region, a method of fluorescent labeling of the strut was discovered using the dye CY3. CY3 served as a hydrophobic tag for purification by hydrophobic interaction chromatography which enabled the separation of labeled and unlabeled species of S1 including a fraction labeled specifically at the strut sequence. The high specificity of labeling was verified by proteolytic digestions, gel electrophoresis, and mass spectroscopy.Analysis of the labeled S1 by collisional quenching, fluorescence polarization, and actinactivated ATPase activity were consistent with predictions from structural models of the probe's location. Although the fluorescent intensity of the CY3 was insensitive to actin binding, its fluorescence polarization was notably affected. Intriguingly, the mobility of the probe increases upon S1 binding to actin suggesting that the CY3 becomes displaced from interactions with the surface of S1 and is consistent with a structural change in the strut due to cleft motions. Labeling the strut reduced the affinity of S1 for actin but did not prevent actin-activated ATPase activity which makes it a potentially useful probe of the actomyosin interface. The different conformations of myosin S1 indicated that the strut is not as flexible as several other key regions of myosin as determined by the application of force constraints to elastic portions of the myosin

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Atomic Structure of Scallop Myosin Subfragment S1 Complexed with MgADP

Cited by 337 publications

References 36 publications

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

Functional regions in the essential light chain of smooth muscle myosin as revealed by the mutagenesis approach

Fluorescence labeling and computational analysis of the strut of myosin’s 50 kDa cleft

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