The degradation of heavy meromyosin by trypsin

Mueller, Helmut; Perry, S. V.

doi:10.1042/bj0850431

Cited by 157 publications

(44 citation statements)

References 16 publications

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“…1 Lower). Lacking the first 787 amino acids of myosin II heavy chain, the chimera is missing most of the globular subfragment-1 domain, which is known to bind and move actin filaments (7)(8)(9). Studying the localization of this chimera enables us to test models of myosin II localization that require myosin II to interact directly with actin filaments, and thus gives us insights into the molecular mechanism of myosin II localization.…”

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Myosin II localization during cytokinesis occurs by a mechanism that does not require its motor domain

Zang

Spudich

1998

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

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Myosin II generates force for the division of eukaryotic cells. The molecular basis of the spatial and temporal localization of myosin II to the cleavage furrow is unknown, although models often imply that interaction between myosin II and actin filaments is essential. We examined the localization of a chimeric protein that consists of the green f luorescent protein fused to the N terminus of truncated myosin II heavy chain in Dictyostelium cells. This chimera is missing the myosin II motor domain, and it does not bind actin filaments. Surprisingly, it still localizes to the cleavage furrow region during cytokinesis. These results indicate that myosin II localization during cytokinesis occurs through a mechanism that does not require it to be the force-generating element or to interact with actin filaments directly.

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Myosin II localization during cytokinesis occurs by a mechanism that does not require its motor domain

Zang

Spudich

1998

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

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“…The two globular heads of myosin, myosin subfragment 1 (Sl), have a central role in this interaction, because they posses two separate sites for binding of actin (A-site) and nucleotide (N-site) and are responsible for ATP hydrolysis (Mueller and Perry, 1962). S1 together with actin and ATP is sufficient to generate movement in vitro (Toyoshima et al, 1987).…”

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Immunochemical Probing of the Functional Role of the 238–246 and 567–574 Sequences of Myosin Heavy Chain

Blotnick

Miller

Gröschel‐Stewart

et al. 1995

European Journal of Biochemistry

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Polyclonal site-directed peptide antibodies were raised against the 567 -574 and 238-246 sequences of the rabbit skeletal muscle myosin heavy chain. These sequences, which are located in the subfragment 1 (Sl) segment of myosin, have been implicated by former studies in actin and nucleotide binding of the molecule and in the communication between the two binding sites. The antibodies obtained from rabbit sera were found to be conformation-sensitive since they specifically reacted with S1 in solid-phase binding assay but not in Western blot. The binding of both antibodies to S1 was strongly inhibited by actin. The antibody against the 567-574 sequence, Abs67-574, moderately decreased the binding of S1 to actin filaments in rigor but not in the weakly-attached state, while Ab,,,-,, did not influence the binding of S l to actin under either conditions. Both antibodies inhibited the actin activation of the MgATPase of S1 but did not affect MgATPase without actin or the Ca-and K(EDTA)-activated ATPase activities of S1. The sliding velocity of actin filaments in the in vitro motility assays were also reduced in the presence of the antibodies. Ab567--574 had especially strong inhibitory effect on the movement of actin filaments. The results indicate that the binding of antibodies may induce conformational changes, which propagate in the S1 structure, perturb the coupling between the binding sites and impair the motor function of myosin.Keywords: myosin; myosin subfragment 1 ; actin; polyclonal antibodies.The interaction of myosin with actin coupled with the hydrolysis of ATP, called cross-bridge cycle in muscle, transforms the chemical energy of ATP into mechanical work. The two globular heads of myosin, myosin subfragment 1 (Sl), have a central role in this interaction, because they posses two separate sites for binding of actin (A-site) and nucleotide (N-site) and are responsible for ATP hydrolysis (Mueller and Perry, 1962). S1 together with actin and ATP is sufficient to generate movement in vitro (Toyoshima et al., 1987). It is generally assumed that the driving force of movement arises from local deformations forced by the ATPase events at the N-site, which are conducted through S1 structure to the A-site, and there compel changes in the S 1 -actin relationship. Actin binding also produces structural changes in S l which affect ATP binding and hydrolysis. Thus, there is coupling between the two binding sites (Botts et al., 1984). It is, therefore, obvious that the characterization of the actin and ATP binding sites of S1 and of the conformational changes which take place in the S1 structure during the myosin -actin interaction, coupled with ATP hydrolysis, has a great significance.

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“….". It is my purpose here to suggest an alternative mechanism, in which the energy derived from ATP hydrolysis can be directly transduced within the filament core.Over the past few years a rather detailed structure for the myosin molecule has emerged from the work of several laboratories (11)(12)(13)(14)(15)(16)(17). Its essential features consist of a two-stranded cable of a-helices, with each strand of the cable folded at one end into an ATPase-active globule.…”

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A Mechanochemical Mechanism for Muscle Contraction

Harrington

1971

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

118

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A mechanism for contraction in skeletal muscle is proposed in which the tension-generating site is located within the core of the thick (myosin) filament, specifically within the trypsin-sensitive hinge region of the myosin rod. The force-developing mechanism is thought to be the transfer of energy from ATP splitting in the globular head of one molecule directly to the hinge region of an adjoining molecule, resulting in a phase transition from crystalline to amorphous within the hinge segment of the second molecule. Binding of MgATP at the actinmyosin interface is considered to be a release mechanism. The model leads to out-of-phase oscillating movement of the cross bridges.In recent years, a large body of literature has accumulated demonstrating that the concept of "melting" during shrinkage and crystallization when polymeric systems are stretched can be regarded as a first-order phase transition, and that dimensional changes in fibrous proteins are intimately related to changes in crystallinity (1,2). A striking illustration of this phenomenon is seen, for example, in the case of a collagen fiber which may undergo abrupt contraction at a characteristic temperature, under a constant small load, to approximately l/6 of its normal, low-temperature length. The transition occurs over a temperature interval of only 2-30C. As is now well documented, the sharpness of the phase transition in the fibril is a macroscopic manifestation of the collagen helix --coil cooperative transformation. The equilibrium between crystalline and amorphous states, as a function of stress on the fiber, follows classical thermodynamic relations (between force, length, and temperature) in which the crystalamorphous phase transition is coupled with dimensional changes. Flory (3) has provided a detailed analysis of the dimensional and force changes to be expected on crystallization of linear polymeric systems and has proposed that a phase transition from an oriented, crystalline to a random, amorphous state underlies muscular contraction. A similar suggestion was put forward by Pryor (4).Consider a length of polymer chain that consists of ordered and disordered segments in which the end points are fixed in space. If the ordered (crystalline) segments are melted, the increased number of conformational states resulting from the increased number of rotatable bonds tends to contract the chain. Since the chain ends are fixed, a force that stems from a rise in conformational entropy of the chain will be generated. rhus, orientation imposed by stretching should promote crystallization, and, conversely, crystallization in a previously oriented polymer should diminish the stress. Although the equilibrium between crystalline and amorphous regions o0 the chain can be displaced with temperature, it is well known that protonation of charged side groups or binding of a charged solute of low molecular weight can also promote a shift in the force-elongation relations as a function of the composition of the external solution. Several authors (3-9) hav...

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The degradation of heavy meromyosin by trypsin

Cited by 157 publications

References 16 publications

Myosin II localization during cytokinesis occurs by a mechanism that does not require its motor domain

Myosin II localization during cytokinesis occurs by a mechanism that does not require its motor domain

Immunochemical Probing of the Functional Role of the 238–246 and 567–574 Sequences of Myosin Heavy Chain

A Mechanochemical Mechanism for Muscle Contraction

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