1. Lecture 24
Tubulin and Microtubule dynamics

5. MW 55000
a-tubulin 8 genes
b-tubulin 9 genes
In humans

9. g-Tubulin Ring Complex

14. Microtubule-associated
proteins (MAPs)
stabilizing
EB1-decorates tips

15. Kinesin was discovered in the cytoplasm of giant squid axon

16. 40 Kinesin genes in humans

20. a, Sample record from the force clamp, showing kinesin-driven bead movement and corresponding optical trap displacement (2 mM ATP). Discrete steps of 8 nm are readily apparent. Inset, schematic representation of the motility assay used. The separation between bead and trap was nominally fixed at x = 175 nm.
Visscher et al., 1999 Nature 400,

21. Stall force = ~5 pN, Mechanical work equals force times distance,
Kinesin-1 has just one binding site per tubulin dimer; the motor takes 8-nm steps from
one tubulin dimer; each step corresponds to one cycle of the ATPase reaction.
                                                        By tethering single molecules of Kinesin-1 to tiny tensiometers - a flexible glass rod or an optical trap - it is possible to measure the force exerted by a single Kinesin-1 molecule.
Stall force = ~5 pN, Mechanical work equals force times distance,
Kinesin-1 can do ~40 x J of work per step, and if there is just one ATP consumed per step, then the efficiency is ~40%.

28. Dynein

30. The Dynactin complex

32. Chlamidomonas
Sperm

35. Cilia/flagella
dynein

38. Intraflagellar transport (IFT)