KINESIN
Microtubules
Questions
• How much ATP is hydrolysed per step?
• How many rate-limiting steps are there?
• What is the mechanism of movement?
Analyse movement
Simulation of randomness
Michaelis-Menten kinetics
v = kcat [ATP]/(Km + [ATP])
When [ATP] is limmiting: v = [ATP] kcat/Km – linear function
Km: Michaelis constant: concentration of ATP at ½vmax
kcat: Velocity at saturatet [ATP]
Kinesin:Km = 62 +/- 8 µMkcat = 680 +/- 31 nm/s
At limiting [ATP]: kcat/Km = 11 +/- 1 nm s-1 µM-1
Randomness parameter
d = step distancex(t) = position
r = 0: Clock-liker = 1: 1 rate-limiting step0 < r < 1: more ratelimiting stepsr > 1: increasing variance (backwards steps, double steps, biochemically inactivatet states)