Lecture 18: Molecular Motors and the use of the Cytoskeleton

Question 1

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

Answer 1

Molecular motor proteins

Question 2

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

Answer 2

mechanochemical

Question 3

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

Answer 3

molecular motors

Question 4

Actin based motors

Answer 4

Myosin

Question 5

Microtubule based motors

Answer 5

Kinesins and Dyneins

Question 6

Kinesin and kinesin-like proteins

Answer 6

Plus-end directed motors

Question 7

Dyneins

Answer 7

Minus-end directed motors

Question 8

The first motor characterized in detail?

Answer 8

Myosin II

Question 9

Myosin II structure

Answer 9

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

Question 10

Myosin II forms ____

Answer 10

bipolar thick filaments

Question 11

Sarcomere

Answer 11

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

Question 12

Sarcomere structure

Answer 12

Question 13

CAP2

Answer 13

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

Question 14

tropomodulin

Answer 14

• binds to the (-) end of actin filament

Question 15

titin

Answer 15

• anchors bipolar thick filaments into Z disc

Question 16

The ___ region of Myosin II is suscepltible to protease cleavage

Answer 16

neck region

Question 17

Myosin II subdomains

Answer 17

Question 18

How does myosin II S1 fragment work?

Answer 18

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

Question 19

The two myosin light chains are similiar in structure to ____

Answer 19

calmodulin

Question 20

The myosin superfamily are…

Answer 20

plus-end directed actin motors

Question 21

Which myosin has minus end movement?

Answer 21

myosin VI

Question 22

The myosin superfamily share a ____

Answer 22

motor domain

Question 23

Kinesin and Kinesin-related proteins are…

Answer 23

plus-end directed microtubule motors

Question 24

Kinesin-1

Answer 24

• best characterized of the kinesins
• globular motor domains

Question 25

Kinesin-5

Answer 25

* forms dimers (polar structures)

Question 26

Kinesin-13

Answer 26

- is a catastrophin (has no motor activity - frays the (+) end of microtubule

Question 27

Kinesin-14

Answer 27

* minus end movement

Question 28

Dyneins

Answer 28

* minus end directed microtubule motors * fastest of the motors

Question 29

What are the two types of Dyneins?

Answer 29

* ciliary * cytoplasmic

Question 30

Dynein structure

Answer 30

Question 31

Acto-myosin Crossbridge Cycle

Answer 31

Question 32

The myosin II ___ is the one responsible for repositioning

Answer 32

lever arm

Question 33

Kinesin mechanochemical cycle

Answer 33

-Kinesin moves hand over hand

Question 34

Kinesin vs. Myosin

Answer 34

* 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.

Question 35

Dynein couples ATP hydrolysis to movement in a different way

Answer 35

Question 36

Dyneins bind to ____ which binds to ___ on vesicles

Answer 36

Myosin V which binds Arp1 on vesicles

Question 37

Myosin V carries cargo along \_\_\_

Answer 37

actin filaments

Question 38

Myosin V transports ___ to dendritic spines

Answer 38

ER

Question 39

Golgi perinuclear localization depends on \_\_\_\_

Answer 39

microtubules

Question 40

Name three actin based structures used for movement

Answer 40

1. filopodia 2. lamellipodia 3. psuedopodia

Question 41

filopodia

Answer 41

– Essential one-dimensional finger-like projection – Similar to microvilli, but more dynamic – Core of long, bundled actin filaments

Question 42

lamellipodia

Answer 42

-Two-dimensional sheet-like structure – Orthogonally cross-linked mesh of actin filaments – Most is known about these due to ease of study by microcopy

Question 43

psuedopodia

Answer 43

– Short three- dimensional projections – Used by neutrophils and macrophages for phagocytosis – Actin filament gel

Question 44

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

Answer 44

Rho, Rac and Cdc42

Question 45

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

Answer 45

* branched actin web in lamellipodia * less stress fiber formation

Question 46

What are the results of downstream Rho-GTP signalling?

Answer 46

* more stress fibers * integrin clustering and focal adhesion formation

Question 47

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

Answer 47

the drug cytochalasin B