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A seesaw model for intermolecular gating in the kinesin motor protein.

Sindelar CV - Biophys Rev (2011)

Bottom Line: Recent structural observations of kinesin-1, the founding member of the kinesin group of motor proteins, have led to substantial gains in our understanding of this molecular machine.The new structural information revises or replaces key details of earlier models of kinesin's ATPase cycle that were based principally on crystal structures of free kinesin, and demonstrates that high-resolution characterization of the kinesin-microtubule complex is essential for understanding the structural basis of the cycle.I discuss the broader implications of the seesaw mechanism within the cycle of a fully functional kinesin dimer and show how the seesaw can account for two types of "gating" that keep the ATPase cycles of the two heads out of sync during processive movement.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, SHMC-E25, 333 Cedar Street, New Haven, CT 06520-8024 USA.

ABSTRACT
Recent structural observations of kinesin-1, the founding member of the kinesin group of motor proteins, have led to substantial gains in our understanding of this molecular machine. Kinesin-1, similar to many kinesin family members, assembles to form homodimers that use alternating ATPase cycles of the catalytic motor domains, or "heads", to proceed unidirectionally along its partner filament (the microtubule) via a hand-over-hand mechanism. Cryo-electron microscopy has now revealed 8-Å resolution, 3D reconstructions of kinesin-1•microtubule complexes for all three of this motor's principal nucleotide-state intermediates (ADP-bound, no-nucleotide, and ATP analog), the first time filament co-complexes of any cytoskeletal motor have been visualized at this level of detail. These reconstructions comprehensively describe nucleotide-dependent changes in a monomeric head domain at the secondary structure level, and this information has been combined with atomic-resolution crystallography data to synthesize an atomic-level "seesaw" mechanism describing how microtubules activate kinesin's ATP-sensing machinery. The new structural information revises or replaces key details of earlier models of kinesin's ATPase cycle that were based principally on crystal structures of free kinesin, and demonstrates that high-resolution characterization of the kinesin-microtubule complex is essential for understanding the structural basis of the cycle. I discuss the broader implications of the seesaw mechanism within the cycle of a fully functional kinesin dimer and show how the seesaw can account for two types of "gating" that keep the ATPase cycles of the two heads out of sync during processive movement.

No MeSH data available.


Overview of kinesin and microtubule architecture. a. Schematic depiction of dimeric kinesin during processive movement. The crystallized conformation of dimeric kinesin-1 (Kozielski et al. 1997) is overlaid on a low-resolution density map of the microtubule with fitted atomic coordinates of α- and β-tubulin from the 2D crystal structure of α-β tubulin (Nogales et al. 1998). The microtubule polarity is indicated with an arrow running towards the plus end. ADP is depicted with yellow spheres. b–d Schematic depiction of structural states encountered by the actively hydrolyzing head in a kinesin dimer as it progresses through ADP, no-nucleotide, and ATP-bound states while attached to the microtubule. The ADP attaches weakly to the microtubule, while no-nucleotide and ATP states are tightly attached states (Rosenfeld et al. 1996). Following the model of Rice et al. (1999), the neck linker is depicted in a disordered conformation in the first two nucleotide states, and is docked along the head towards the microtubule plus end in the ATP state. e, f Overview of the atomic structure of kinesin-1 obtained by X-ray crystallography and fitted into a high-resolution cryo-EM map together with the atomic structure of tubulin (Sindelar and Downing 2010). Key structural elements are labeled
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Fig1: Overview of kinesin and microtubule architecture. a. Schematic depiction of dimeric kinesin during processive movement. The crystallized conformation of dimeric kinesin-1 (Kozielski et al. 1997) is overlaid on a low-resolution density map of the microtubule with fitted atomic coordinates of α- and β-tubulin from the 2D crystal structure of α-β tubulin (Nogales et al. 1998). The microtubule polarity is indicated with an arrow running towards the plus end. ADP is depicted with yellow spheres. b–d Schematic depiction of structural states encountered by the actively hydrolyzing head in a kinesin dimer as it progresses through ADP, no-nucleotide, and ATP-bound states while attached to the microtubule. The ADP attaches weakly to the microtubule, while no-nucleotide and ATP states are tightly attached states (Rosenfeld et al. 1996). Following the model of Rice et al. (1999), the neck linker is depicted in a disordered conformation in the first two nucleotide states, and is docked along the head towards the microtubule plus end in the ATP state. e, f Overview of the atomic structure of kinesin-1 obtained by X-ray crystallography and fitted into a high-resolution cryo-EM map together with the atomic structure of tubulin (Sindelar and Downing 2010). Key structural elements are labeled

Mentions: More than two decades of intensive study have established that the kinesin motor domain undergoes the following biochemical transitions during its ATPase cycle (Fig. 1): (1) weak attachment to the microtubule in the motor’s ADP-bound form; (2) release of ADP to form a tightly attached motor–microtubule complex; (3) binding of ATP, which triggers a significant conformational rearrangement of the motor domain, associated with a displacement of the cargo attachment point (the "neck linker", see below) in the direction of travel; and (4) hydrolysis of ATP and release of phosphate, which leads to concurrent detachment of the motor domain from the microtubule (Gilbert and Johnson 1994; Ma and Taylor 1995).Fig. 1


A seesaw model for intermolecular gating in the kinesin motor protein.

Sindelar CV - Biophys Rev (2011)

Overview of kinesin and microtubule architecture. a. Schematic depiction of dimeric kinesin during processive movement. The crystallized conformation of dimeric kinesin-1 (Kozielski et al. 1997) is overlaid on a low-resolution density map of the microtubule with fitted atomic coordinates of α- and β-tubulin from the 2D crystal structure of α-β tubulin (Nogales et al. 1998). The microtubule polarity is indicated with an arrow running towards the plus end. ADP is depicted with yellow spheres. b–d Schematic depiction of structural states encountered by the actively hydrolyzing head in a kinesin dimer as it progresses through ADP, no-nucleotide, and ATP-bound states while attached to the microtubule. The ADP attaches weakly to the microtubule, while no-nucleotide and ATP states are tightly attached states (Rosenfeld et al. 1996). Following the model of Rice et al. (1999), the neck linker is depicted in a disordered conformation in the first two nucleotide states, and is docked along the head towards the microtubule plus end in the ATP state. e, f Overview of the atomic structure of kinesin-1 obtained by X-ray crystallography and fitted into a high-resolution cryo-EM map together with the atomic structure of tubulin (Sindelar and Downing 2010). Key structural elements are labeled
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3117274&req=5

Fig1: Overview of kinesin and microtubule architecture. a. Schematic depiction of dimeric kinesin during processive movement. The crystallized conformation of dimeric kinesin-1 (Kozielski et al. 1997) is overlaid on a low-resolution density map of the microtubule with fitted atomic coordinates of α- and β-tubulin from the 2D crystal structure of α-β tubulin (Nogales et al. 1998). The microtubule polarity is indicated with an arrow running towards the plus end. ADP is depicted with yellow spheres. b–d Schematic depiction of structural states encountered by the actively hydrolyzing head in a kinesin dimer as it progresses through ADP, no-nucleotide, and ATP-bound states while attached to the microtubule. The ADP attaches weakly to the microtubule, while no-nucleotide and ATP states are tightly attached states (Rosenfeld et al. 1996). Following the model of Rice et al. (1999), the neck linker is depicted in a disordered conformation in the first two nucleotide states, and is docked along the head towards the microtubule plus end in the ATP state. e, f Overview of the atomic structure of kinesin-1 obtained by X-ray crystallography and fitted into a high-resolution cryo-EM map together with the atomic structure of tubulin (Sindelar and Downing 2010). Key structural elements are labeled
Mentions: More than two decades of intensive study have established that the kinesin motor domain undergoes the following biochemical transitions during its ATPase cycle (Fig. 1): (1) weak attachment to the microtubule in the motor’s ADP-bound form; (2) release of ADP to form a tightly attached motor–microtubule complex; (3) binding of ATP, which triggers a significant conformational rearrangement of the motor domain, associated with a displacement of the cargo attachment point (the "neck linker", see below) in the direction of travel; and (4) hydrolysis of ATP and release of phosphate, which leads to concurrent detachment of the motor domain from the microtubule (Gilbert and Johnson 1994; Ma and Taylor 1995).Fig. 1

Bottom Line: Recent structural observations of kinesin-1, the founding member of the kinesin group of motor proteins, have led to substantial gains in our understanding of this molecular machine.The new structural information revises or replaces key details of earlier models of kinesin's ATPase cycle that were based principally on crystal structures of free kinesin, and demonstrates that high-resolution characterization of the kinesin-microtubule complex is essential for understanding the structural basis of the cycle.I discuss the broader implications of the seesaw mechanism within the cycle of a fully functional kinesin dimer and show how the seesaw can account for two types of "gating" that keep the ATPase cycles of the two heads out of sync during processive movement.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, SHMC-E25, 333 Cedar Street, New Haven, CT 06520-8024 USA.

ABSTRACT
Recent structural observations of kinesin-1, the founding member of the kinesin group of motor proteins, have led to substantial gains in our understanding of this molecular machine. Kinesin-1, similar to many kinesin family members, assembles to form homodimers that use alternating ATPase cycles of the catalytic motor domains, or "heads", to proceed unidirectionally along its partner filament (the microtubule) via a hand-over-hand mechanism. Cryo-electron microscopy has now revealed 8-Å resolution, 3D reconstructions of kinesin-1•microtubule complexes for all three of this motor's principal nucleotide-state intermediates (ADP-bound, no-nucleotide, and ATP analog), the first time filament co-complexes of any cytoskeletal motor have been visualized at this level of detail. These reconstructions comprehensively describe nucleotide-dependent changes in a monomeric head domain at the secondary structure level, and this information has been combined with atomic-resolution crystallography data to synthesize an atomic-level "seesaw" mechanism describing how microtubules activate kinesin's ATP-sensing machinery. The new structural information revises or replaces key details of earlier models of kinesin's ATPase cycle that were based principally on crystal structures of free kinesin, and demonstrates that high-resolution characterization of the kinesin-microtubule complex is essential for understanding the structural basis of the cycle. I discuss the broader implications of the seesaw mechanism within the cycle of a fully functional kinesin dimer and show how the seesaw can account for two types of "gating" that keep the ATPase cycles of the two heads out of sync during processive movement.

No MeSH data available.