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BIOC 341 > Lecture 18: Molecular Motors and the use of the Cytoskeleton > Flashcards

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

1
Q

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

A

Molecular motor proteins

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2
Q

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

A

mechanochemical

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3
Q

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

A

molecular motors

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4
Q

Actin based motors

A

Myosin

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5
Q

Microtubule based motors

A

Kinesins and Dyneins

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6
Q

Kinesin and kinesin-like proteins

A

Plus-end directed motors

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7
Q

Dyneins

A

Minus-end directed motors

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8
Q

The first motor characterized in detail?

A

Myosin II

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9
Q

Myosin II structure

A
  • one of the most abundant proteins in the body
  • other proteins associate at neck region
  • long tail is composed of coiled-coiled secondary structure
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10
Q

Myosin II forms ____

A

bipolar thick filaments

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11
Q

Sarcomere

A
  • dark band = myosin II thick filaments
  • light band = actin (thin filaments)
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12
Q

Sarcomere structure

A
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13
Q

CAP2

A
  • actin binding protein, binds to (+) end of actin filament
  • in Z disc of sarcomere
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14
Q

tropomodulin

A
  • binds to the (-) end of actin filament
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15
Q

titin

A
  • anchors bipolar thick filaments into Z disc
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16
Q

The ___ region of Myosin II is suscepltible to protease cleavage

A

neck region

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17
Q

Myosin II subdomains

A
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18
Q

How does myosin II S1 fragment work?

A
  • myosin light chains wrap around the alphahelical segment to change position for substrate binding
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19
Q

The two myosin light chains are similiar in structure to ____

A

calmodulin

20
Q

The myosin superfamily are…

A

plus-end directed actin motors

21
Q

Which myosin has minus end movement?

A

myosin VI

22
Q

The myosin superfamily share a ____

A

motor domain

23
Q

Kinesin and Kinesin-related proteins are…

A

plus-end directed microtubule motors

24
Q

Kinesin-1

A
  • best characterized of the kinesins
  • globular motor domains
25
Q

Kinesin-5

A
  • forms dimers (polar structures)
26
Q

Kinesin-13

A
  • is a catastrophin (has no motor activity
  • frays the (+) end of microtubule
27
Q

Kinesin-14

A
  • minus end movement
28
Q

Dyneins

A
  • minus end directed microtubule motors
  • fastest of the motors
29
Q

What are the two types of Dyneins?

A
  • ciliary
  • cytoplasmic
30
Q

Dynein structure

A
31
Q

Acto-myosin Crossbridge Cycle

A
32
Q

The myosin II ___ is the one responsible for repositioning

A

lever arm

33
Q

Kinesin mechanochemical cycle

A

-Kinesin moves hand over hand

34
Q

Kinesin vs. Myosin

A
  • 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
Q

Dynein couples ATP hydrolysis to movement in a different way

A
36
Q

Dyneins bind to ____ which binds to ___ on vesicles

A

Myosin V which binds Arp1 on vesicles

37
Q

Myosin V carries cargo along ___

A

actin filaments

38
Q

Myosin V transports ___ to dendritic spines

A

ER

39
Q

Golgi perinuclear localization depends on ____

A

microtubules

40
Q

Name three actin based structures used for movement

A
  1. filopodia
  2. lamellipodia
  3. psuedopodia
41
Q

filopodia

A

– Essential one-dimensional finger-like projection

– Similar to microvilli, but more dynamic

– Core of long, bundled actin filaments

42
Q

lamellipodia

A

-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
Q

psuedopodia

A

– Short three- dimensional projections

– Used by neutrophils and macrophages for phagocytosis

– Actin filament gel

44
Q

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

A

Rho, Rac and Cdc42

45
Q

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

A
  • branched actin web in lamellipodia
  • less stress fiber formation
46
Q

What are the results of downstream Rho-GTP signalling?

A
  • more stress fibers
  • integrin clustering and focal adhesion formation
47
Q

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

A

the drug cytochalasin B

BIOC 341 (24 decks)

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