Reversible movement of switch 1 loop of myosin determines actin interaction

Kintses, Bálint; Gyimesi, Máté; Pearson, David; Geeves, Michael A.; Zeng, Wei; Bagshaw, Clive R.; Málnási‐Csizmadia, András

doi:10.1038/sj.emboj.7601482

Cited by 46 publications

(79 citation statements)

References 31 publications

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“…(ii) The present calculations are also supported by data from Kintses et al (22), who had shown that the light scattering signal changes from actin dissociation covary with the signals from switch-1 closing (fluorescence of W239 þ ). This observation suggests that the u50 domain and switch 1 move simultaneously, consistent with the present observation that they belong to the same semirigid unit.…”

Section: Discussionsupporting

confidence: 77%

“…This setup has been described previously in detail by Koppole et al (19) Molecular Kinematics. The timescale of the ATP-induced dissociation of rigor myosin from actin is in the millisecond range (5,22), beyond the scope of unconstrained molecular dynamics simulations. Applying constraints along some predefined reaction coordinate to accelerate the simulation tends to favor events correlating strongly with this predefined reaction coordinate, thus biasing the sequence of events upon which a description of the mechanism is to be based (33).…”

Section: Methodsmentioning

confidence: 99%

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Structural mechanism of the ATP-induced dissociation of rigor myosin from actin

Kühner

Fischer

2011

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

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Myosin is a true nanomachine, which produces mechanical force from ATP hydrolysis by cyclically interacting with actin filaments in a four-step cycle. The principle underlying each step is that structural changes in separate regions of the protein must be mechanically coupled. The step in which myosin dissociates from tightly bound actin (the rigor state) is triggered by the 30 Å distant binding of ATP. Large conformational differences between the crystal structures make it difficult to perceive the coupling mechanism. Energetically accessible transition pathways computed at atomic detail reveal a simple coupling mechanism for the reciprocal binding of ATP and actin.chemomechanical coupling | conformational transition | conjugate peak refinement | muscle contraction | power-stroke M otility as well as intracellular transport are essential functions in all organisms, from unicellulars to highest eukaryotes. They are driven by molecular motors, which convert the chemical energy of ATP hydrolysis into mechanical force (1). One family of motors are myosins, which drive processes like cytokinesis, vesicle transport, and muscle contraction by walking along actin fibrils (2).The N-terminal globular domain of myosin (called the head) contains all the functional domains (i.e., the ATP binding site, the actin-binding regions, and the rotating "converter" domain). It is able to hydrolyze ATP and move along an actin filament on its own (3). The cyclic interaction of myosin and actin to create motion is known as the Lymn-Taylor cycle (4) (Fig. 1A). The principle underlying each of the four Lymn-Taylor steps is that structural change in one region of the protein is tightly coupled to change in another domain of the protein. This sort of welldefined coupling between parts of the motor really is the essence of any type of motor (for instance, the motions of the valve and the piston are coupled in a car engine). The key to understanding how myosin works as a nanomachine is to understand in each Lymn-Taylor step how the structural information is communicated from one part of myosin to another (much like finding the crankshaft and the timing belt in the engine analogy).The focus here is on the rigor-dissociation step (Fig. 1A, I → II), in which, upon binding ATP, the head dissociates from the actin fibril and goes from the rigor state (thus called for the stiffness of corpses when ATP gets depleted in muscle cells) to the prerecovery (also known as postrigor) state (kinetic relaxation time approximately 10 ms in excess ATP; ref. 5). In this step, small changes in the ATP binding site are coupled to large structural changes in the 30-Å distant actin-binding domain that substantially reduce binding affinity for actin (6, 7), thus leading to the dissociation. We describe that mechanism at atomic detail using simulations of the conformational transition between the rigor and the postrigor states and present molecular movies of the energetically accessible transition pathways (SI Text). Fig. 1B shows the rigor-like crystal structure of...

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Section: Discussionsupporting

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Structural mechanism of the ATP-induced dissociation of rigor myosin from actin

Kühner

Fischer

2011

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

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“…We show for the first time an actin-dependent closure of switch I in the ADP state that has only been observed in smooth muscle myosin to date, because actin has been shown to open switch I in skeletal and Dictyostelium discoideum myosin where it has been studied previously (19,40). Although it is unclear how actin binding causes closure of switch I, this conformation is most likely stablilized by the specific binding between actin and smooth muscle myosin.…”

Section: Discussionmentioning

confidence: 92%

“…The two states showed a temperature-dependent equilibrium between them, favoring the closed conformation of the active site at lower temperatures. There is also kinetic evidence from different myosin isoforms, indicating the presence of multiple actomyosin-ADP states (17)(18)(19)(20). In smooth muscle myosin, strong binding to both actin and ADP has been proposed to be necessary for the formation of the latch state, where a decrease in regulatory light chain phosphorylation leads to maintained tension for long periods of time with little hydrolysis of ATP (21) and which may be related to the closed active site state previously observed at low temperature by EPR and transient kinetics (16 -19).…”

mentioning

confidence: 99%

Switch I Closure Simultaneously Promotes Strong Binding to Actin and ADP in Smooth Muscle Myosin

Decarreau

James

Chrin

et al. 2011

Journal of Biological Chemistry

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The motor protein myosin uses energy derived from ATP hydrolysis to produce force and motion. Important conserved components (P-loop, switch I, and switch II) help propagate small conformational changes at the active site into large scale conformational changes in distal regions of the protein. Structural and biochemical studies have indicated that switch I may be directly responsible for the reciprocal opening and closing of the actin and nucleotide-binding pockets during the ATPase cycle, thereby aiding in the coordination of these important substrate-binding sites. Smooth muscle myosin has displayed the ability to simultaneously bind tightly to both actin and ADP, although it is unclear how both substrate-binding clefts could be closed if they are rigidly coupled to switch I. Here we use single tryptophan mutants of smooth muscle myosin to determine how conformational changes in switch I are correlated with structural changes in the nucleotide and actin-binding clefts in the presence of actin and ADP. Our results suggest that a closed switch I conformation in the strongly bound actomyosin-ADP complex is responsible for maintaining tight nucleotide binding despite an open nucleotide-binding pocket. This unique state is likely to be crucial for prolonged tension maintenance in smooth muscle.Myosin is a molecular motor that uses energy derived from ATP hydrolysis to produce force and motion along an actin filament during muscle contraction and other forms of cell motility. The myosin motor domain consists of a 95-kDa globular domain containing separate actin and nucleotide-binding sites and is connected to an extended 85-Å-long ␣-helix, termed the lever arm, which is important in generating force and motion by undergoing a rotation called the powerstroke (1-7) (Fig. 1). To ensure efficient energy transduction, the mechanical powerstroke is tightly coupled to the enzymatic ATPase cycle of myosin, with the nucleotide state of the active site dictating both the lever arm position and myosin interaction with actin.The active site of myosin shows remarkable similarity to that of G-proteins as well as motor kinesin (8, 9). The principle components of this active site architecture are a seven-stranded ␤-sheet comprising the core of the binding pocket and three flexible loops known as the P-loop, switch I, and switch II, which coordinate the bound nucleotide (7, 10). Although conformational changes in the P-loop are generally not observed in structural studies, switches I and II have been shown to undergo significant changes in conformation based on the presence or absence of the ␥-phosphate of the bound nucleotide (3, 10). Small changes in active site switch positions are propagated into larger rearrangements in distal regions of the motor with switch I thought to affect the actin-binding cleft and switch II thought to affect the position of the lever arm (11).The actin-binding cleft is located within the 50-kDa tryptic fragment of the myosin motor domain (7). This subdomain can be divided into two components known as ...

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“…Specifically, how tightly coupled is the communication pathway from the actin interface to the nucleotide pocket or to the force-generating domain? There is evidence for coupling between the actin-binding cleft and nucleotide pocket (63)(64)(65), as well as between the nucleotide pocket and the force-generating domain (66,67). Recent work suggests that there is direct coupling between the actin-binding interface, particularly the myosin activation loop, and the relay helix in the myosin force-generating domain (68).…”

Section: Discussionmentioning

confidence: 99%

Conformationally Trapping the Actin-binding Cleft of Myosin with a Bifunctional Spin Label

Moen

Thomas

Klein

2013

Journal of Biological Chemistry

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Background:The actin-binding cleft of myosin is proposed to close upon force generation. Results: Crosslinking the cleft with a bifunctional spin-label weakens binding, eliminates actin activation, and disorders the actomyosin interface. Conclusion: Restricting the cleft traps an actomyosin state with structural dynamics intermediate between strongly and weakly bound. Significance: We have determined the structural dynamics of an elusive intermediate at the threshold of force generation.

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Reversible movement of switch 1 loop of myosin determines actin interaction

Cited by 46 publications

References 31 publications

Structural mechanism of the ATP-induced dissociation of rigor myosin from actin

Structural mechanism of the ATP-induced dissociation of rigor myosin from actin

Switch I Closure Simultaneously Promotes Strong Binding to Actin and ADP in Smooth Muscle Myosin

Conformationally Trapping the Actin-binding Cleft of Myosin with a Bifunctional Spin Label

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