Molecular Machines

Kinesin

The 28 review prompts from the notes on Kinesin. Answer each in your head, then reveal it. Your grade decides when the card comes back.

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Summary 8

Read this section: Summary, in the Kinesin notes

  1. Which way along a microtubule does kinesin-1 carry its cargo?

  2. Which part of kinesin-1 docks onto the head when ATP binds and pulls the partner head forward?

  3. Plus-end and minus-end kinesins have nearly identical cores. Which part of a kinesin sets the direction it walks?

  4. Kinesin-1's centre of mass moves blank per step, the length of one tubulin dimer.

  5. About how many steps does a single kinesin-1 take before it lets go of the microtubule?

  6. With no load, kinesin-1 walks at about 800 nm/s, so one turnover takes about blank.

  7. In a kinesin 'molecular shuttle', what does the kinesin do?

  8. Unlike kinesin, how does a designed protein motor (a protease-coated hub) move across a peptide lawn?

How it works 8

Read this section: How it works, in the Kinesin notes

  1. In kinesin-1, blank to the bound head makes its neck linker zip onto the head.

  2. Why do ATP binding and neck-linker docking go together in a kinesin-1 head?

  3. In a kinesin-1 step, blank carries the free head forward; neck-linker docking only sets the direction.

  4. What makes a kinesin-1 head release its ADP?

  5. A kinesin-1 head holding blank binds the track only weakly, so it can search or let go.

  6. Why does kinesin-1 stay on the track for about 100 steps instead of falling off after one?

  7. When kinesin-1 splits its ATP is still argued. What does tracking single heads at 1,000 frames per second suggest?

  8. Under a heavy opposing load, why does kinesin-1's free head land behind its partner instead of ahead?

Big picture 5

Read this section: Big picture, in the Kinesin notes

  1. If proteins made near the spine just drifted down a 1 m nerve cell, they would need about blank to reach the foot.

  2. About how long does fast outward transport take to carry cargo 1 m along a nerve cell?

  3. A single kinesin falls off after about 1 µm. How does cargo still finish a 1 m trip down an axon?

  4. The 'walker with two feet' picture of kinesin gets hand-over-hand stepping right. What does it get wrong about the free foot?

  5. On a cargo vesicle in an axon, which motor pulls against kinesin, back toward the cell body?

Evidence 7

Read this section: Evidence, in the Kinesin notes

  1. How did Svoboda and colleagues (1993) first see kinesin's 8 nm steps?

  2. Yildiz and colleagues put one dye on one head of kinesin. What pattern of dye movement showed that kinesin walks hand over hand?

  3. How did Coy and colleagues (1999) show that kinesin takes one step per ATP?

  4. In Carter and Cross's optical trap, kinesin-1 took as many back steps as forward steps near blank of opposing load.

  5. Visscher and colleagues (1999) measured kinesin's stall force at different ATP levels. What did they find?

  6. Why does extra positive charge on kinesin's neck coiled coil make its runs longer?

  7. In Milic and colleagues' force-clamp runs, what effect of added phosphate showed that kinesin's processivity is gated by phosphate release?

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