Dimerization of the Head–Rod Junction of Scallop Myosin

Málnási‐Csizmadia, András; Shimony, Ethan; Hegyi, György; Szent‐Györgyi, Albert; Nyitray, László

doi:10.1006/bbrc.1998.9603

Cited by 19 publications

(14 citation statements)

References 33 publications

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“…Different muscle types have fine-tuned S2 stability to different extents, as evidenced by the observation that N-terminal fragments of native scallop myosin S2 shorter than 340 residues fail to dimerize (13), whereas the 126-residue fragment of human cardiac ␤-myosin II described here, S2-⌬, can be isolated as a stable dimer after expression in Escherichia coli (5). A comparison of S2 sequences from different species and tissues reveals strong sequence variation in the first three heptads; however, overall features such as charge distribution or the positioning of noncanonical residues in a and d positions are relatively conserved (Fig.…”

Section: Resultsmentioning

confidence: 99%

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Blankenfeldt

Thomä

Wray

et al. 2006

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

100

132

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Myosin II is the major component of the muscle thick filament. It consists of two N-terminal S1 subfragments (''heads'') connected to a long dimeric coiled-coil rod. The rod is in itself twofold symmetric, but in the filament, the two heads point away from the filament surface and are therefore not equivalent. This breaking of symmetry requires the initial section of the rod, subfragment 2 (S2), to be relatively flexible. S2 is an important functional element, involved in various mechanisms by which the activity of smooth and striated muscle is regulated. We have determined crystal structures of the 126 N-terminal residues of S2 from human cardiac ␤-myosin II (S2-⌬), of both WT and the disease-associated E924K mutant. S2-⌬ is a straight parallel dimeric coiled coil, but the N terminus of one chain is disordered in WT-S2-⌬ due to crystal contacts, indicative of unstable local structure. Bulky noncanonical side chains pack into a͞d positions of S2-⌬'s N terminus, leading to defined local asymmetry and axial stagger, which could induce nonequivalence of the S1 subfragments. Additionally, S2 possesses a conserved charge distribution with three prominent rings of negative potential within S2-⌬, the first of which may provide a binding interface for the ''blocked head'' of smooth muscle myosin in the OFF state. The observation that many disease-associated mutations affect the second negatively charged ring further suggests that charge interactions play an important role in regulation of cardiac muscle activity through myosin-binding protein C.coiled coil ͉ muscle ͉ crystallography ͉ regulation ͉ familial hypertrophic cardiomyopathy M uscle contraction results from the ATP-dependent cyclic interaction of the proteins myosin II and actin, assembled in thick and thin filaments, respectively. Myosin II consists of two heavy chains, each of which binds one essential and one regulatory light chain (Fig.

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Section: Resultsmentioning

confidence: 99%

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Blankenfeldt

Thomä

Wray

et al. 2006

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

100

132

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“…The first hypothesis (Vibert andCraig, 1982, 1985;Vibert et al, 1986) is supported by data and modeling showing that 1) the head-rod junction (the neck) of the myosin molecule is flexible (Málnási-Csizmadia et al, 1998;Li et al, 2003), 2) Ca ++ binding likely changes neck flexibility (Houdusse and Cohen, 1996;Málnási-Csizmadia et al, 1999) (although see Wells and Bagshaw, 1984b), 3) the two myosin heads can lie alongside one another (Offer and Knight, 1996), 4) the ATP and Ca ++ binding sites of the two heads communicate in the 'off' state (Kalabokis and Szent-Györgyi, 1997;Azzu et al, 2006), EDTA increases the extent to which the two heads show correlated movement (Wells and Bagshaw, 1983), and 6) in the absence of Ca ++ the heads are highly ordered and primarily extend towards the tail (Vibert and Craig, 1985;Craig, 1989, 1992;Stafford III et al, 2001;Zhao and Craig, 2003a). The idea is that in the absence of Ca ++ the heads interact with one another and are thus prevented from interacting with the thin filament, and Ca ++ -induced changes in the flexibility of the myosin neck (where the regulatory complex is located) frees the heads to act independently.…”

Section: 411mentioning

confidence: 89%

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

126

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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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“…However, it is worth noting that earlier work using a 93 amino acid peptide from the coiled-coil forming region of scallop muscle myosin-2 also gave rise to an APCC structure (53), but this was known to form a parallel coiled-coil in the context of the full-length molecule (54). At present, the resolution of our negatively stained EMs, obtained using recombinant M10HMM with the leucine zipper sequence after amino acid 936, does not allow us to discern the tail structure directly.…”

Section: Discussionmentioning

confidence: 99%

Myosin-10 produces its power-stroke in two phases and moves processively along a single actin filament under low load

Takagi

Farrow

Billington

et al. 2014

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

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Myosin-10 is an actin-based molecular motor that participates in essential intracellular processes such as filopodia formation/ extension, phagocytosis, cell migration, and mitotic spindle maintenance. To study this motor protein's mechano-chemical properties, we used a recombinant, truncated form of myosin-10 consisting of the first 936 amino acids, followed by a GCN4 leucine zipper motif, to force dimerization. Negative-stain electron microscopy reveals that the majority of molecules are dimeric with a head-to-head contour distance of ∼50 nm. In vitro motility assays show that myosin-10 moves actin filaments smoothly with a velocity of ∼310 nm/s. Steady-state and transient kinetic analysis of the ATPase cycle shows that the ADP release rate (∼13 s −1 ) is similar to the maximum ATPase activity (∼12-14 s −1 ) and therefore contributes to rate limitation of the enzymatic cycle. Single molecule optical tweezers experiments show that under intermediate load (∼0.5 pN), myosin-10 interacts intermittently with actin and produces a power stroke of ∼17 nm, composed of an initial 15-nm and subsequent 2-nm movement. At low optical trap loads, we observed staircaselike processive movements of myosin-10 interacting with the actin filament, consisting of up to six ∼35-nm steps per binding interaction. We discuss the implications of this load-dependent processivity of myosin-10 as a filopodial transport motor.actomyosin | stable single alpha-helix | optical trapping | myosin X | myosin-5a

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Dimerization of the Head–Rod Junction of Scallop Myosin

Cited by 19 publications

References 33 publications

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

Crystal structures of human cardiac β-myosin II S2-Δ provide insight into the functional role of the S2 subfragment

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

Myosin-10 produces its power-stroke in two phases and moves processively along a single actin filament under low load

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