Regulated Conformation of Myosin V

Wang, Fei; Thirumurugan, Kavitha; Stafford, Walter F.; Hammer, John A.; Knight, Peter J.; Sellers, James R.

doi:10.1074/jbc.c300488200

Cited by 160 publications

(173 citation statements)

References 39 publications

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“…It has been shown that the activation of myosin Va by Ca 2ϩ is accompanied by a transition from a folded conformation (14S in the absence of Ca 2ϩ ) to an open conformations (11S in the presence of Ca 2ϩ ) (6)(7)(8). We took two approaches to investigate the effect of D134A and D136A mutations on the conformational changes of myosin Va.…”

Section: Resultsmentioning

confidence: 99%

“…It was found that Ca 2ϩ -activation of the ATPase activity of myosin-Va is accompanied by a large conformational transition, from a 14S folded conformation in the absence of Ca 2ϩ to an 11S open conformation in the presence of micromolar Ca 2ϩ (6)(7)(8). In contrast, myosin Va heavy meromyosin (HMM), a constitutively active fragment lacking the C-terminal globular tail domain, is not well regulated by Ca 2ϩ and does not undergo a large conformational transition like fulllength myosin Va (6)(7)(8). These results suggest that the tail domain plays a key role in the Ca 2ϩ -dependent regulation of myosin Va by inhibiting the ATPase of the head.…”

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confidence: 99%

“…These results suggest that the tail domain plays a key role in the Ca 2ϩ -dependent regulation of myosin Va by inhibiting the ATPase of the head. Based on these findings, a tail-inhibition model for the regulation of myosin Va has been proposed (6)(7)(8). In this model, myosin Va in the inhibited state is in a folded conformation such that the tail domain interacts with and inhibits myosin Va motor activity; high Ca 2ϩ or cargo binding may reduce the interaction between the head and tail domains, thus activating motor activity.…”

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confidence: 99%

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The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

Li¹,

Jung

Wang³

et al. 2008

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

109

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Myosin Va is a well known processive motor involved in transport of organelles. A tail-inhibition model is generally accepted for the regulation of myosin Va: inhibited myosin Va is in a folded conformation such that the tail domain interacts with and inhibits myosin Va motor activity. Recent studies indicate that it is the C-terminal globular tail domain (GTD) that directly inhibits the motor activity of myosin Va. In the present study, we identified a conserved acidic residue in the motor domain (Asp-136) and two conserved basic residues in the GTD (Lys-1706 and Lys-1779) as critical residues for this regulation. Alanine mutations of these conserved charged residues not only abolished the inhibition of motor activity by the GTD but also prevented myosin Va from forming a folded conformation. We propose that Asp-136 forms ionic interactions with Lys-1706 and Lys-1779. This assignment locates the GTD-binding site in a pocket of the motor domain, formed by the N-terminal domain, converter, and the calmodulin in the first IQ motif. We propose that binding of the GTD to the motor domain prevents the movement of the converter/lever arm during ATP hydrolysis cycle, thus inhibiting the chemical cycle of the motor domain.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

Li¹,

Jung

Wang³

et al. 2008

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

109

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“…By analogy with some class II myosins, for which the lever arm plays a regulatory function, it is plausible that the LCBD of myosin V also serves a regulatory role. In agreement with this view, a number of reports uncover a regulatory effect of Ca 2ϩ and CaM on the conformation and activity of myosin V that could involve the LCBD directly (21)(22)(23)(24)(25). Inhibition of the ATPase activity of myosin V after increases in Ca 2ϩ concentration has been attributed to the dissociation of CaM from the heavy chain (26) and͞or a conformational change in CaM (27).…”

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confidence: 79%

Structure of the light chain-binding domain of myosin V

Terrak

Rębowski

et al. 2005

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

118

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Myosin V is a double-headed molecular motor involved in organelle transport. Two distinctive features of this motor, processivity and the ability to take extended linear steps of Ϸ36 nm along the actin helical track, depend on its unusually long light chainbinding domain (LCBD). The LCBD of myosin V consists of six tandem IQ motifs, which constitute the binding sites for calmodulin (CaM) and CaM-like light chains. Here, we report the 2-Å resolution crystal structure of myosin light chain 1 (Mlc1p) bound to the IQ2-IQ3 fragment of Myo2p, a myosin V from Saccharomyces cerevisiae. This structure, combined with FRET distance measurements between probes in various CaM-IQ complexes, comparative sequence analysis, and the previously determined structures calmodulin ͉ IQ motif ͉ x-ray crystallography ͉ FRET M yosin V is a molecular motor involved in a range of organelle-transporting functions, including the transport of melanosomes and synaptic vesicles in mammals and vacuoles and mRNA in yeast (1-4). Myosin V is composed of two identical heavy chains and 12 light chains. Each heavy chain consists of an N-terminal motor domain, containing the actinbinding and ATP catalytic sites, followed by the light chainbinding domain (LCBD), formed by six IQ motifs in tandem, and the tail domain, composed of regions of coiled-coil and a globular domain involved in cargo binding. The coiled-coil regions mediate the association of the heavy chains into dimers. The IQ motifs are Ϸ25-aa segments, centered around the consensus sequence IQxxxRGxxxR, and constitute the binding sites for the light chains, which can be either calmodulin (CaM) or CaM-related molecules (5, 6).A number of features distinguish myosin V from other myosin families. Myosin V has a high duty cycle, defined as the property to remain attached to actin for a large fraction of the mechanochemical cycle (7-9). The high duty cycle of myosin V is explained by a slow rate of ADP release, which becomes the rate-limiting step in the ATPase cycle (7). This kinetic adaptation allows myosin V to take multiple steps without dissociating from the actin filament, that is, myosin V is a processive motor (10-12). Linked with processivity is the ability of myosin V to take large steps of Ϸ36 nm (10), a distance equal to the helical repeat of the actin filament. Such a step size allows myosin V to walk in a straight line on the actin filament, in a hand-over-hand fashion (13-16). These characteristics seem to adapt myosin V for its cellular function, the transport of large cargoes atop the actin filament while avoiding collisions with cellular structures (3). Yet, central to this motor's uniqueness is its unusually long LCBD (4). A number of laboratories have recently established a direct connection between the length and structural integrity of the LCBD and the step size and processivity of myosin V (4,(17)(18)(19)(20). These studies focus on the role of the LCBD as a passive structural device whose function is to amplify small nucleotidedependent motions originating in the motor doma...

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“…Our results suggest that this complex modulates SNARE-dependent interactions and regulates at least the exocytosis of dense-core vesicles by forming a link between vesicles and their targets; in other words, the complex regulates the recruitment of the vesicles to the readily releasable pool during sustained secretion. Recently, the Ca 2ϩ /CaM-dependent interaction between the cargo-conveying tail and the head of myosin-Va was shown to be an important factor regulating its conformation (Krementsov et al, 2004;Li et al, 2004Li et al, , 2005Wang et al, 2004). Ca 2ϩ /CaM is an important regulator of both exocytosis and the cargo-conveying activity of myosin-Va, and further studies of this novel interaction should help elucidate the roles of myosin-Va in Ca 2ϩ -regulated exocytosis.…”

Section: Discussionmentioning

confidence: 99%

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

Watanabe

Nomura

Ohyama

et al. 2005

MBoC

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Myosin-Va is an actin-based processive motor that conveys intracellular cargoes. Synaptic vesicles are one of the most important cargoes for myosin-Va, but the role of mammalian myosin-Va in secretion is less clear than for its yeast homologue, Myo2p. In the current studies, we show that myosin-Va on synaptic vesicles interacts with syntaxin-1A, a t-SNARE involved in exocytosis, at or above 0.3 M Ca 2؉ . Interference with formation of the syntaxin-1A-myosin-Va complex reduces the exocytotic frequency in chromaffin cells. Surprisingly, the syntaxin-1A-binding site was not in the tail of myosin-Va but rather in the neck, a region that contains calmodulin-binding IQ-motifs. Furthermore, we found that syntaxin-1A binding by myosin-Va in the presence of Ca 2؉ depends on the release of calmodulin from the myosin-Va neck, allowing syntaxin-1A to occupy the vacant IQ-motif. Using an anti-myosin-Va neck antibody, which blocks this binding, we demonstrated that the step most important for the antibody's inhibitory activity is the late sustained phase, which is involved in supplying readily releasable vesicles. Our results demonstrate that the interaction between myosin-Va and syntaxin-1A is involved in exocytosis and suggest that the myosin-Va neck contributes not only to the large step size but also to the regulation of exocytosis by Ca 2؉ . INTRODUCTIONMyosin-V, a processive molecular motor, conveys vesicles and other organelles along F-actin (Mercer et al., 1991;Espreafico et al., 1992;Cheney et al., 1993;Reck-Peterson et al., 2000;Vale, 2003). This unconventional myosin is a member of the class-V myosins, which are expressed in all eukaryotic species from yeast to mammals (Reck-Peterson et al., 2000;Matsui, 2003;Vale, 2003). Myosin-V is a dimeric protein (Cheney et al., 1993). Each monomer is composed of a head region, a long neck domain containing six tandem IQ-motifs, and a tail region (Reck-Peterson et al., 2000). The head acts as a plus-end ATPase-dependent molecular motor to move myosin-V along F-actin (Reck-Peterson et al., 2000). The long neck region is thought to act as a lever arm to regulate the motor activity of the head and to maintain the large step size of myosin-V via bound light chains. In higher eukaryotes, the light chains consist mainly of calmodulin (CaM) bound to the IQ-motifs in the neck domain (Cheney et al., 1993;Vale, 2003). In addition, the globular tail of myosin-V interacts with membrane-bound vesicles. In these ways, myosin-V plays a central role in intracellular polarized transport (Reck-Peterson et al., 2000;Matsui, 2003;Vale, 2003).Among the three isoforms of myosin-V in higher vertebrates, myosin-Va is the most abundant, and it is highly enriched in the brain (Espreafico et al., 1992), particularly in the neurons (Tilelli et al., 2003). Several lines of evidence indicate that synaptic vesicles, which undergo the Ca 2ϩ -regulated exocytosis, are one of the most important cargoes for myosin-Va (Prekeris and Terrian, 1997;Bridgman, 1999;Tilelli et al., 2003). In addition, Myo2p, a yeast h...

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Regulated Conformation of Myosin V

Cited by 160 publications

References 39 publications

The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

Structure of the light chain-binding domain of myosin V

Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A

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Regulated Conformation of Myosin V

Cited by 160 publications

References 39 publications

The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

The globular tail domain puts on the brake to stop the ATPase cycle of myosin Va

Structure of the light chain-binding domain of myosin V

Myosin-Va Regulates Exocytosis through the Submicromolar Ca2+-dependent Binding of Syntaxin-1A

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Myosin-Va Regulates Exocytosis through the Submicromolar Ca²+-dependent Binding of Syntaxin-1A