1. Lecture # 13: Biological Actuators 1) Osmotic motors2) Bacterial rotors 3) Molecular rack and pinions 4) striated muscles

2. www.niwascience.co.nz www.jcu.edu.au trigger high Ca2+ H 2 0 influx high osmotic pressure 1. Osmotic Motors e.g. nematocyst http://upload.wikimedia.org Cnidarians: Jellyfish Corals Hydroids

3. www.gay-dive.com

4. 2. Bacterial Rotors ‘run & tumble’ behavior During run, flagella spin in same direction. During tumble, one or more flagella change direction. Howard Berg

5. E.Coli uses a ‘biased random walk’ to search for food in a complex 3D landscape.

6. www.arn.org rigid ‘rotor’ composed of many proteins reconstruction from Electron Micrograph artist’s reconstruction structure of bacterial rotor ‘stator’ rigid filament ‘rotor axis’ Key features of bacterial rotors: only true ‘wheel’ in Nature driven by proton pump ~400 steps/rotation operates at ~ 50 Hz super efficient (90%) 40 nm

7. 3. Molecular ‘Rack and Pinions’ www.sparknotes.com Eukaryotic cells possess a complex cytoskeleton: actin network throughout cell microtubules associated with nucleus These two structural systems are associated with specifc motors.

8. Structure of actin and tubulin filaments

9. Two motors run on tubulin: kinesin and dynein -+ kinesin dynein tubulin binding site ATP binding cleft converter domain cable cargo attachment operates as ‘hand-over-hand’ dimer

10. dynein has special role as cilia/flagella motor

11. myosin has structure similar to kinesin

12. myosin plays important role in muscle contraction

13. sliding filament model sarcomere

15. electro-mechanical coupling

17. Ca 2+ binds here

18. Lecture # 13: Biological Actuators 1) Osmotic motors2) Bacterial rotors 3) Molecular rack and pinions 4) striated muscles