Linear ATPase MotorsMitotic Spindle OrganizationCilia and Flagella Assembly and DynamicsFormation of Golgi and ER NetworksVesicle TransportMolecular MotorsProteins that use chemical free energy (e.g. from ATP hydrolysis) to perform mechanical workIntroduction to Motor ProteinsLinear MotorsCytoskeletal proteins, that consume ATP in order to walk on polymeric tracks (generating pNforces)exhibit: nanometer scale actuation, directed motion, range of transport length scalesStructural FeaturesLinear motors have a high degree of homology, and share many design featuresKinesinStalkMotor DomainNeck Linker Light ChainsPolymer Tracks: The RoadsACTINMICROTUBULE8nm100 kDa ProteinHow long will it take a 100kDa protein to take a diffusion limited step like kinesin?(assume 1-dimensional confinement)Transport in Crowded Cellular EnvironmentsThermal RatchetsGenerating Deterministic MotionFor a review see:Asymmetric PotentialCoupled motorsATP catalysisMyosin VSpeed: 350 nm/s ATPase: 5.0 1/sKinesinSpeed: 850 nm/s ATPase: 100.0 1/sDyneinSpeed: -1250 nm/s ATPase: 2.0 1/s**ALL INVOLVED IN VESICLE TRANSPORT**Magenta: Catalytic CoreGreen: Polymer Binding siteCommon Structural Components of Linear MotorsFull Length KinesinVelocity(MOTILITY EXPERIMENTS)** Lmand Kmdo not have to be the same value **Measuring Catalysis and Motility ATPase rate(FROM SOLUTION)dP/dt = SKM+ S(Kinesin and Myosin Have Functional Differences in their ATPase Cycles)Kinesin: Myosin:Comparing ATP Hydrolysis Rates and Polymer Binding(Myosin has a low duty ratio - biochemical evidence)Comparing the Duty Ratio and Working Distance of Kinesin and MyosinUnderstanding the Connection between Hydrolysis and MotionDifferent Myosin molecules have different working distancesBringing It All TogetherHow Do We Measure Motor Dynamics?• All motors are not equal from an experimental perspective (Why kinesin is an ideal motor for study)• Measuring motor steps and forces• Bringing it all together: Understanding Dynamic Assembly Using Molecular MotorsGenerating Motor DirectionalityTypes: ncd - minus end-directed meiotic motor performs a spindle pole function in meiosis, organizing the ends of spindle microtubules into poles. kinesin - positive end-directed motor Functions in Spindle and Chromosome motility and Organelle / Vesicle Transport (c-Terminal Motor)kinesin ncdDirectionality is not due to the nature of the Motor DomainThe “Gear Box” and Forming DimersDimerization domain does not seem to be a lever armRequired for directionality and processivitySo-called neck linker is thought to communicate strain to trailing head causing it to release from the microtubuleActinbinding sitelever arm(however, this module is shorter than the distance between steps)Measuring Single Molecule Steps(Kinesin)Dye is 7nm from center of massMeasuring Single Molecule Steps(Myosin)Leibler Science 2002Two MotorsIncreasing Kinesin Conc.Understanding Motor-Based Self-Assemblygoing beyond single molecule dynamicsBeyond Single Moledules cont.Same is observed in sperm flagellaHow do cells divide?What determines the shape and spatial organization of
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