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MSDF > Myosin Motion > Flashcards

Myosin Motion Flashcards

1
Q

Which direction does myosin VI move?

A

towards the minus end

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2
Q

Which direction does myosin V move?

A

Towards the plus end

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3
Q

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

A

How many light chains bind

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4
Q

What is the function of myosin V?

A

Membrane trafficking

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5
Q

What kind of duty ratio does Myosin V have?

A

High duty

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6
Q

What is the structure of myosin V?

A
  • 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
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7
Q

How many IQ motifs does myosin V contain?

A

6

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8
Q

What tracks does myosin V use?

A
  • Cytoskeletal actin monomer proteins
  • 2 strand helical bundle
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9
Q

How frequently do equivalent binding sites occur on cytoskeletal actin?

A

Every 36nm

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10
Q

What kind of mechanism does myosin V use?

A

Hand-over hand movement

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11
Q

How far does myosin V cargo move in one step?

A

36nm

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12
Q

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

A

72nm

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13
Q

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

A

FIONA

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14
Q

What function does the light chain serve in myosin V?

A

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

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15
Q

What does the converter domain transition between?

A

Pre and post stroke configurations

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16
Q

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

A

70º

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17
Q

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

A

~37nm

18
Q

What is the rate limiting step for Myosin V?

A

ADP release

19
Q

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

A

Once ATP has been hydrolysed and when ADP is still bound

20
Q

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

A

Directly after ATP hydrolysis

21
Q

When is myosin V unbound from actin?

A

During ATP hydrolysis

22
Q

What happens after the power stroke?

A

The protein enters a strained waiting state

23
Q

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

A

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

24
Q

What couples the ATP cycles in myosin V?

A

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

25
Q

What causes accerlation of ADP release in myosin V?

A

Mechanical strain

26
Q

What are the similarities between myosin V and kinesin?

A
  • processive dimer of 2 motors
  • directional movement along track
  • hand-over-hand mech requiring coordination
  • 1 ATP used per step
  • High duty
27
Q

How many ATP are used per step in myosin V?

A

1

28
Q

What are the differences between myosin V and kinesin?

A
  • Myosin V much larger step size
  • different tracks and binding sites
  • Quite different coupling
29
Q

What is the function of myosin VI?

A

Involved in membrane trafficking

30
Q

Which direction does myosin VI move?

A

Towards the minus end

31
Q

What mechanism does myosin VI use?

A

Hand-over-hand

32
Q

What is the structure of myosin VI?

A
  • dimer of 2 heavy chains and multiple light chains
  • N-terminal globular myosin motor domain and special insert domain after converter
  • Coiled-coil structure
33
Q

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

A

Special insert

34
Q

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

A

1

35
Q

What allows myosin VI to move backwards?

A

Special insert domain

36
Q

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

A
  1. Introduces a kink in the helix
  2. Alters the angle between pre and post powerstroke states
37
Q

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

A
  • Reverses orientation of lever arm, reversing pre and post stroke positions
  • alters angle between pre and post stroke states
38
Q

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

A

180º

39
Q

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

A

The minus end

40
Q

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

A

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

MSDF (30 decks)

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