molecular motors and intracellular transport.pdf

Molecular motors and intracellular transport Joyjyoti Das, Ph.D. Assistant Professor  Learning outcomes  To gain knowledge on the structure and function of various molecular motors in the cell  To gain knowle...

Molecular motors and intracellular transport Joyjyoti Das, Ph.D. Assistant Professor  Learning outcomes  To gain knowledge on the structure and function of various molecular motors in the cell  To gain knowledge on intracellular transport How Does Intracellular Molecular-Motor-Driven Transport Work? A Cell Is Like a City Workers Proteins Power Plant Mitochondria Roads Actin fibers, microtubules Trucks Kinesin, dynein, myosin Factories Ribosomes Library Genome Recycling center Lysosome Police Chaperones Post office Golgi apparatus Communications Signaling networks Intracellular Traffic  How is intracellular transport regulated? © Scientific American  Microtubules (MT) are like freeways and actin filaments are like local surface streets. Dispersion: Spread of cargoes throughout the cell Aggregation: Bring cargoes back to nucleus Motor proteins Myosin Kinesin Motor proteins move cargo along filaments Molecular Biology of the Cell, 3rd Ed, 1994 Biochemistry, 4ht Ed, 1995 Myosins Are a family of motor proteins that bind to & move along actin filaments toward the + ends. Large globular heads bind and split ATP Undergo a configurational change that changes the angle of the head with respect to an a-helical tail. E.g. Myosin II Myosin II of vertebrate muscle Myosin cross-bridge cycle MT-based Motors: Kinesin & Dynein Kinesin is a large protein with 4 polypeptide chains Like myosin it has 2 heavy chains, each with a globular head domain and long a-helical tail. 2 light chains on cargo- MT binding end binding (vary in diff. cells w diff. cargo) ATP-binding site Coiled-coil in each head tail  Dyneins are a family of minus end directed MT motors. Largest and fastest molecular motors (14 mm/sec vs 2 mm/sec for kinesin) Dynein moves vesicles and the Golgi app toward the cell center. Comparison of kinesin and myosin mechanochemical cycles