Myosin Motion

Question 1

Which direction does myosin VI move?

Answer 1

towards the minus end

Question 2

Which direction does myosin V move?

Answer 2

Towards the plus end

Question 3

What does the number of IQ motifs in the lever arm of myosin dictate?

Answer 3

How many light chains bind

Question 4

What is the function of myosin V?

Answer 4

Membrane trafficking

Question 5

What kind of duty ratio does Myosin V have?

Answer 5

High duty

Question 6

What is the structure of myosin V?

Answer 6

• Active as dimer of heavy chains
• N-terminal globular myosin motor ATPase
• 6 IQ motifs with binding sites for light chains
• C-terminal globular cargo binding domain and further light chains

Question 7

How many IQ motifs does myosin V contain?

Answer 7

6

Question 8

What tracks does myosin V use?

Answer 8

• Cytoskeletal actin monomer proteins
• 2 strand helical bundle

Question 9

How frequently do equivalent binding sites occur on cytoskeletal actin?

Answer 9

Every 36nm

Question 10

What kind of mechanism does myosin V use?

Answer 10

Hand-over hand movement

Question 11

How far does myosin V cargo move in one step?

Answer 11

36nm

Question 12

For one step how far does the myosin V motor move?

Answer 12

72nm

Question 13

What technique was used to label the myosin V cargo and motor?

Answer 13

FIONA

Question 14

What function does the light chain serve in myosin V?

Answer 14

The light chain binding region serves as a lever arm to amplify movements of the converter domain

Question 15

What does the converter domain transition between?

Answer 15

Pre and post stroke configurations

Question 16

What is the angle between the pre- and post- stroke converter domain in myosin V?

Answer 16

70º

Question 17

In myosin V the long lever arm results in displacement of lever arm by what distance?

Answer 17

~37nm

Question 18

What is the rate limiting step for Myosin V?

Answer 18

ADP release

Question 19

At what point in the ATPase cycle does the power stroke occur in myosin V?

Answer 19

Once ATP has been hydrolysed and when ADP is still bound

Question 20

In myosin V when does the lever arm move to the pre-stroke position?

Answer 20

Directly after ATP hydrolysis

Question 21

When is myosin V unbound from actin?

Answer 21

During ATP hydrolysis

Question 22

What happens after the power stroke?

Answer 22

The protein enters a strained waiting state

Question 23

Why does partial execution of the power stroke occur in myosin V?

Answer 23

it can’t complete it due to the other motor being in the ADP bound state

Question 24

What couples the ATP cycles in myosin V?

Answer 24

The ADP bound motor being pulled by mechanical force of the powerstroke, entering the strained waiting state

Question 25

What causes accerlation of ADP release in myosin V?

Answer 25

Mechanical strain

Question 26

What are the similarities between myosin V and kinesin?

Answer 26

* processive dimer of 2 motors * directional movement along track * hand-over-hand mech requiring coordination * 1 ATP used per step * High duty

Question 27

How many ATP are used per step in myosin V?

Answer 27

1

Question 28

What are the differences between myosin V and kinesin?

Answer 28

* Myosin V much larger step size * different tracks and binding sites * Quite different coupling

Question 29

What is the function of myosin VI?

Answer 29

Involved in membrane trafficking

Question 30

Which direction does myosin VI move?

Answer 30

Towards the minus end

Question 31

What mechanism does myosin VI use?

Answer 31

Hand-over-hand

Question 32

What is the structure of myosin VI?

Answer 32

* dimer of 2 heavy chains and multiple light chains * N-terminal globular myosin motor domain and special insert domain after converter * Coiled-coil structure

Question 33

What is the main structural difference between myosin V and myosin VI?

Answer 33

Special insert

Question 34

How many IQ motifs does the lever arm of myosin VI contain?

Answer 34

1

Question 35

What allows myosin VI to move backwards?

Answer 35

Special insert domain

Question 36

What are the effects of the special insert in myosin VI?

Answer 36

1. Introduces a kink in the helix 2. Alters the angle between pre and post powerstroke states

Question 37

What is the effect of a kink in the lever arm of myosin VI?

Answer 37

* Reverses orientation of lever arm, reversing pre and post stroke positions * alters angle between pre and post stroke states

Question 38

In myosin VI the kink the lever arm makes the angle between the pre and post stroke states what?

Answer 38

180º

Question 39

In myosin VI which direction does the post stroke state point to?

Answer 39

The minus end

Question 40

How can myosin VI contact actin binding sites 36nm apart?

Answer 40

3 helix bundle proximal tail can undergo an unfolding transition which allows it to stretch and extend the short lever arm