The structural basis of myosin V processive movement as revealed by electron cryomicroscopy.

The Program of Cell Adhesion, The Burnham Institute, La Jolla, California 92037, USA.
Molecular Cell (Impact Factor: 14.46). 10/2005; 19(5):595-605. DOI: 10.1016/j.molcel.2005.07.015
Source: PubMed

ABSTRACT The processive motor myosin V has a relatively high affinity for actin in the presence of ATP and, thus, offers the unique opportunity to visualize some of the weaker, hitherto inaccessible, actin bound states of the ATPase cycle. Here, electron cryomicroscopy together with computer-based docking of crystal structures into three-dimensional (3D) reconstructions provide the atomic models of myosin V in both weak and strong actin bound states. One structure shows that ATP binding opens the long cleft dividing the actin binding region of the motor domain, thus destroying the strong binding actomyosin interface while rearranging loop 2 as a tether. Nucleotide analogs showed a second new state in which the lever arm points upward, in a prepower-stroke configuration (lever arm up) bound to actin before phosphate release. Our findings reveal how the structural elements of myosin V work together to allow myosin V to step along actin for multiple ATPase cycles without dissociating.

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    ABSTRACT: 1. Introduction 2. Principle of AFM Imaging 3. Speed Limits of AFM Imaging 4. Minimizing Invasiveness: The Tip–Sample Interaction 5. Small Cantilevers 6. Hydrodynamic Pressure 7. Substrate Surfaces7.1. Mica Surfaces 7.2. Lipid Bilayer Surfaces 7.3. Surface of 2D Crystals of Streptavidin 8. Dynamic Imaging of Proteins8.1. General Remarks on Dynamic Structural Study of Motor Proteins 8.2. Myosin V Walking on Actin Filament8.2.1. Visualization of Lever-Arm Swing 8.2.2. Directional Rule 8.2.3. Foot Stomp and Tension Generation 8.2.4. Asymmetric ADP Dissociation Kinetics 8.2.5. Chemo-mechanical Coupling in Walking Myosin V 8.2.6. Remaining Issues in the Walking Mechanism of Myosin V 8.3. Rotary Catalysis of α3β3 Subcomplex of F1-ATPase 8.4. General Remarks on Membrane Proteins 8.5. Structural Changes of Membrane Proteins8.5.1. Bacteriorhodopsin Responding to Light 8.5.2. Role of Trimer–Trimer Interaction in bR Function 8.5.3. Up–Down Motion of Ca2+-ATPase 8.5.4. P2X4 Receptor in Response to ATP 8.6. Diffusion and Interaction of Membrane Proteins8.6.1. Interaction between bR Trimers in 2D Crystal Lattice 8.6.2. Interaction of C-Rings in Purple Membrane 8.6.3. Interaction of AQP0 in Native Eye Lens Membrane 8.6.4. Diffusion and Interaction of OmpF 8.7. Self-Assembly Processes8.7.1. Amyloid Fibril Formation 8.7.2. 2D Crystallization of Annexin A5 8.7.3. Supported Lipid Bilayer Formation 8.8. Other Topics on Protein Dynamics8.8.1. Cellulase 8.8.2. Intrinsically Disordered Proteins 8.8.3. Dynamics of Vacancy Defects in 2D Crystals of Proteins 9. Dynamic Imaging of Live Cells9.1. Bacterial Cell Surfaces9.1.1. Bacteriolysis of Bacillus subtilis Subjected to Lysozyme 9.1.2. Surface Change of E. coli Subjected to Antimicrobial Peptide 9.1.3. Imaging of Single Molecules on Live Bacteria Surfaces 9.2. Dynamic Phenomena Occurring on Eukaryotic Cell Surfaces 9.3. Diffusion and Interactions of Membrane Proteins on Eukaryotic Live Cells 10. Perspectives 11. Concluding Remarks
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    ABSTRACT: Although class IX myosins are single-headed, they demonstrate characteristics of processive movement along actin filaments. Double-headed myosins that move processively along actin filaments achieve this by successive binding of the two heads in a hand-over-hand mechanism. This mechanism, obviously, cannot operate in single-headed myosins. However, it has been proposed that a long class IX specific insertion in the myosin head domain at loop2 acts as an F-actin tether, allowing for single-headed processive movement. Here, we tested this proposal directly by analysing the movement of deletion constructs of the class IX myosin from Caenorhabditis elegans (Myo IX). Deletion of the large basic loop2 insertion led to a loss of processive behaviour, while deletion of the N-terminal head extension, a second unique domain of class IX myosins, did not influence the motility of Myo IX. The processive behaviour of Myo IX is also abolished with increasing salt concentrations. These observations directly demonstrate that the insertion located in loop2 acts as an electrostatic actin tether during movement of Myo IX along the actin track.
    PLoS ONE 01/2014; 9(1):e84874. · 3.53 Impact Factor


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