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Lecture 6 Biomotors Self assembling rotary motors.

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Presentation on theme: "Lecture 6 Biomotors Self assembling rotary motors."— Presentation transcript:

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 ADP + Phosphate ATP + H 2 O ATPase - the movie

7 What does the whole motor look like?

8 The proton-driven torque generator

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

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

11 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  subunit rotation. (A)-(A’) are potential energies for the corresponding chemical states in a. Adapted from ref. 7. Average torque during each revolution is 50pN.nm, but this is distributed over sub- steps. ATPase is a variable step stepper motor

12 Montemagno Lab Science (2000) 290, p1555 Nature Materials (2002) 1, p173 Zn 2+ control of motor Molecular baton twirling

13 Cell motility is driven by larger ion-driven molecular motors Bacterial Flagellar

14 Flagellar

15 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 Force/speed measurements on Flagellar - twirling cells

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