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Lecture 6 Biomotors

Lecture 6 Biomotors. Self assembling rotary motors. Examples of Biomolecular Motors. Karplus and Gao, Curr Opin. Struct. Biol (2004) 250-259. Proton gradients generated by electron transfer. The smallest rotary motor self-assembles from 8 proteins. ATPase has identifiable motor parts.

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Lecture 6 Biomotors

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  1. Lecture 6 Biomotors Self assembling rotary motors

  2. Examples of Biomolecular Motors Karplus and Gao, Curr Opin. Struct. Biol (2004) 250-259

  3. Proton gradients generated by electron transfer

  4. The smallest rotary motor self-assembles from 8 proteins

  5. ATPase has identifiable motor parts Motor, Drive shaft, Cam, Stator, Viscous coupling,

  6. ATPase - the movie ADP + Phosphate ATP + H2O

  7. What does the whole motor look like?

  8. The proton-driven torque generator

  9. Single molecule motor nanotechnology Kinosita Lab Nature (1997) 386, 299-302

  10. ATPase is a stepper motor Kinosita Lab Nature (2001) 410, 898-904

  11. ATPase is a variable step stepper motor Average torque during each revolution is 50pN.nm, but this is distributed over sub-steps. Substeps in the rotation of F1-ATPase at 20 µM ATP. Long dashed lines are drawn at intervals of 120˚, and dotted lines are drawn 30˚ below the dashed lines. Kinetics of substeps (a) and deduced rotational potential (b). Colored lines in b represent the angle dependent potential energy for g subunit rotation. (A)-(A’) are potential energies for the corresponding chemical states in a. Adapted from ref. 7.

  12. Molecular baton twirling Montemagno Lab Science (2000) 290, p1555 Nature Materials (2002) 1, p173 Zn2+ control of motor

  13. Cell motility is driven by larger ion-driven molecular motorsBacterial Flagellar

  14. Flagellar

  15. Force/speed measurements on Flagellar - twirling cells Driving Force Proton or sodium electrochemical gradient Number of Protons per revolution ~ 1000 (energy per proton) ~ 2.5 x 10-20 J (6kT) Maximum rotation rate 300 Hz (protons) 1700 Hz (sodium) Torque at stall ~ 4 x 10-18 Nm (4nN.nm) Maximum power output ~ 10-15 W Efficiency 50-100% (stall) ~ 5% (swimming cell) Number of steps per revolution ~ 50 per torque generator Linear velocity of cells <100µm s-1

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