Motor proteins, cellular motility Regulation of actin treadmilling

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04/10/2013 Motor proteins • Proteins that can bind to specific filaments • chemo-mechanical enzymes (mechanochemical coupling) − they hydrolyze ATP (chemical energy) − they can produce kinetic energy • Their thermodynamic efficiency is between 30 and 60%. • They convert chemical energy to mechanical work directly. • The cytoskeletal filaments: − Serve as tracks to carry organelles or vesicles − Can be moved by the motor proteins Families of motor proteins Cytoskeletal motors • Actin-based motors (myosins) • Microtubule based motors (kinesins and dyneins) Non-cytoskeletal motors • Nucleic acid based (DNA and RNA polymerases, helicases) • Rotary motors: bacterial flagellum, FI-F0-ATPase 2
04/10/2013 Basic components of the cytoskeletal transport system • Motor − Myosin, kinesin, dynein • Track − Microfilaments, microtubules • Cargo − organelles, chromosomes, vesicles • Fuel − ATP, GTP Common properties Structure • N-terminal globular head: motor domain − nucleotide binding and hydrolysis − specific binding sites for the corresponding filaments • C-terminal: structural and functional role with specificity N C Mechanical properties, function In principle: cyclic function and work Motor → binding to a filament → force → dissociation → relaxation 1 cycle requires 1 ATP hydrolysis They can either move or produce force 3
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Motor proteins, cellular motility Regulation of actin treadmilling

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