Molecular Machines

Myosin

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

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Summary 7

Read this section: Summary, in the Myosin notes

  1. Myosin classes share the same head. Name the three things that differ between them.

  2. In a myosin head, what does the long lever-arm helix do with the rotation of the converter?

  3. What does the coiled-coil tail of myosin do?

  4. What is the duty ratio of a myosin head?

  5. Muscle myosin spends only a small fraction of its cycle bound to actin. How does muscle still pull steadily?

  6. Omecamtiv mecarbil activates cardiac myosin and mavacamten inhibits it. What do the two drugs have in common at the structure level?

  7. Both cardiac myosin drugs completed phase 3 trials, and regulators have approved blank.

How it works 8

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

  1. When a primed myosin head first docks on actin, why can phosphate not leave yet?

  2. In the myosin power stroke, the converter rotates and the lever swings through about blank, mostly along the filament.

  3. Why does ATP binding make a myosin head let go of actin?

  4. What does a myosin head do during the recovery stroke, off actin?

  5. Which step sets the walking pace of myosin-5?

  6. Why does a single myosin-5 head spend about 70% of its cycle strongly bound to actin?

  7. Why do the two heads of myosin-5 bind actin 13 subunits apart?

  8. In a two-headed myosin-5 on actin, what holds the lead head's lever in the primed position after it releases phosphate?

Big picture 6

Read this section: Big picture, in the Myosin notes

  1. In muscle, how do myosins add their forces, and how do sarcomeres add their shortening?

  2. Muscle is like train carriages coupled in a row. What does this analogy get wrong about the sarcomere?

  3. Myosin heads are like a rowing crew. Where does this analogy break down?

  4. From the phosphate in a myosin head to the hand, movement grows about blank times.

  5. Calcium switches myosin on. How does SERCA switch it off?

  6. Myosin and kinesin share almost no sequence identity. What do they share?

Evidence 7

Read this section: Evidence, in the Myosin notes

  1. How did Finer, Simmons and Spudich (1994) measure the step of a single myosin molecule?

  2. Finer 1994 found a stroke of about 11 nm for muscle myosin. What stroke did Molloy 1995 find for a single head (S1)?

  3. Yildiz and colleagues tracked one dye on the lever of myosin-5. What step pattern showed that it walks hand over hand?

  4. What did Uyeda, Abramson and Spudich (1996) find when they changed the neck length of Dictyostelium myosin?

  5. How did De La Cruz and colleagues measure how much of the cycle a myosin-5 head stays strongly bound?

  6. In single-molecule stepping of myosin-5 (Rief 2000), what showed that ADP release gates each step?

  7. How did Klebl and colleagues (2025) see myosin-5 both before and after its stroke on actin?

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