motors

Question 1

myosin general structure (4)

Answer 1

1. ATP-binding pocket,
2. Actin-binding interface
3. Converter domain
4. Catalytic domain connected to lever arm

Question 2

lever arm purpose

Answer 2

allows motor to move by pivoting with respect to the tail of the myosin, moving the actin filament
Also, it binds to two light chains that prevent myosin aggregation and increase lever arm stiffness

Question 3

which motor takes longer steps?

Answer 3

myosin-V at 36nm, tx as long as myosin II

Question 4

describe the mechanochemical coupling of ATP hydrolysis and myosin mvmt

Answer 4

myosin binds ATP and releases from actin, myosin then hydrolyzes ATP to ADP and cocks its head into pre-stroke state, ready to bind an actin filament. When myosin finds actin, it binds weakly, then locks on tightly, triggering phosphate release. As phosphate is released, myosin II lever arm changes conformation, generating force and work to move myosin into ADP-bound state, and now myosin is load bearing. Myosin releases ADP and goes into rigor state, short lived in healthy cells

Question 5

duty ratio

Answer 5

the ratio of the strongly bound state time vs the total ATPase cycle time

Question 6

what do kinesins and dyneins use as tracks

Answer 6

microtubules

Question 7

what powers the work step of kinesin?

Answer 7

binding of ATP