Lecture 18: Molecular Motors and the use of the Cytoskeleton Flashcards Preview

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Flashcards in Lecture 18: Molecular Motors and the use of the Cytoskeleton Deck (47):
1

________ are used to convert the chemical energy of ATP hydrolysis to mechanical motion.

Molecular motor proteins

2

They undergo a ____ cycle of filament binding, conformational change, and filament release.

mechanochemical

3

____ are used for diverse processes from muscle contraction to vesicle movement.

molecular motors

4

Actin based motors

Myosin

5

Microtubule based motors

Kinesins and Dyneins

6

Kinesin and kinesin-like proteins

Plus-end directed motors

7

Dyneins

Minus-end directed motors

8

The first motor characterized in detail?

Myosin II

9

Myosin II structure

  • one of the most abundant  proteins in the body
  • other proteins associate at neck region
  • long tail is composed of coiled-coiled secondary structure

A image thumb
10

Myosin II forms ____

bipolar thick filaments

11

Sarcomere

  • dark band = myosin II thick filaments
  • light band = actin (thin filaments)

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12

Sarcomere structure

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13

CAP2

  • actin binding protein, binds to (+) end of actin filament
  • in Z disc of sarcomere

14

tropomodulin

  • binds to the (-) end of actin filament

15

titin

  • anchors bipolar thick filaments into Z disc

16

The ___ region of Myosin II is suscepltible to protease cleavage

neck region

17

Myosin II subdomains

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18

How does myosin II S1 fragment work?

  • myosin light chains wrap around the alphahelical segment to change position for substrate binding

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19

The two myosin light chains are similiar in structure to ____

calmodulin

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20

The myosin superfamily are...

plus-end directed actin motors

21

Which myosin has minus end movement?

myosin VI

22

The myosin superfamily share a ____

motor domain

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23

Kinesin and Kinesin-related proteins are...

plus-end directed microtubule motors

24

Kinesin-1

  • best characterized of the kinesins
  • globular motor domains

25

Kinesin-5

  • forms dimers (polar structures)

26

Kinesin-13

-is a catastrophin (has no motor activity

-frays the (+) end of microtubule

27

Kinesin-14

  • minus end movement

28

Dyneins

  • minus end directed microtubule motors
  • fastest of the motors

29

What are the two types of Dyneins?

  • ciliary
  • cytoplasmic

30

Dynein structure

A image thumb
31

Acto-myosin Crossbridge Cycle

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32

The myosin II ___ is the one responsible for repositioning

lever arm

33

Kinesin mechanochemical cycle

-Kinesin moves hand over hand

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34

Kinesin vs. Myosin

  • Kinesin binds tightly to microtubules with bound ATP 
  •  Myosin binds tightly to actin without nucleotide (rigor state). 
  • The different in the time of attachment to actin allows many myosins to work in conjunction with each other. 

35

Dynein couples ATP hydrolysis to movement in a different way 

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36

Dyneins bind to ____ which binds to ___ on vesicles

Myosin V which binds Arp1 on vesicles

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37

Myosin V carries cargo along ___

actin filaments

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38

Myosin V transports ___ to dendritic spines

ER

39

Golgi perinuclear localization depends on ____

microtubules

40

Name three actin based structures used for movement

  1. filopodia
  2. lamellipodia
  3. psuedopodia

41

filopodia

– Essential one-dimensional finger-like projection

– Similar to microvilli, but more dynamic 

– Core of long, bundled actin filaments

42

lamellipodia

  -Two-dimensional sheet-like structure 

– Orthogonally cross-linked mesh of actin filaments 

– Most is known about these due to ease of study by microcopy 

43

psuedopodia

– Short three- dimensional projections 

– Used by neutrophils and macrophages for phagocytosis 

– Actin filament gel 

44

Small G-proteins that respond to various extracellular signals to alter the actin cytoskeleton? 

Rho, Rac and Cdc42

45

What are the results of downstream signaling of Rac-GTP?

  • branched actin web in lamellipodia
  • less stress fiber formation

46

What are the results of downstream Rho-GTP signalling?

  • more stress fibers
  • integrin clustering and focal adhesion formation

47

____ caps the plus end of actin filaments (and prevents further elongation)

 the drug cytochalasin B