Slide 002: "Cell motility" [ 00:00:26 ]
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Protein Polymers, Crawling Cells, and Comet Tails
Cell motility
Four types of biological motors
Cell structure depends on protein filaments
Actin filament structure
Actin filament polymerization
Most cells in the human body are bacteria
Actin-based motility of the intracellular bacterial pathogen Listeria monocytogenes
Listeria monocytogenes actin-rich clouds and tails in cytoplasmic extract
What do we understand?
What don t we understand?
Force generation by protein polymerization: Thermodynamics
What can we do?
What can we do?
Movement of L. monocytogenes in cytoplasmic extracts
High-resolution tracking
Trajectories of 1000 bacteria
Trajectories of 1000 bacteria
Speeds vary significantly among genetically identical individuals
For each individual, speed and actin density both fluctuate
Cross-correlations between speed and actin density fluctuations
What can we do?
Movement of ActA-coated beads
Movement of ActA-coated beads in cytoplasmic extract
Symmetry is broken by variations in actin dynamic behavior
Elastic Brownian ratchet model
Stochastic model for symmetry-breaking based on the elastic Brownian ratchet
The simple 2-D stochastic model reproduces qualitative aspects of symmetry-breaking
Actin polymerization distorts vesicles
Movement of ellipsoidal beads
Two preferred orientations
What can we do?
How will we dissect the molecular basis of these complex mechanics?
Listeria monocytogenes ActA site-directed mutagenesis
Mechanical phenotype 1: Change in path persistence
Mechanical phenotype 2: Skidding
What about cell crawling?
Symmetry-breaking in fish skin cells
Conclusions
Acknowledgements