Final: Ch 17 Myosin Flashcards Preview

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Flashcards in Final: Ch 17 Myosin Deck (69):
1

what are myosins

actin-based motor proteins that move along actin filaments

convert energy from ATP hydrolysis into movement along actin

2

myosin II

found in skeletal muscle

hundreds of molecules assemble into bundles

3

myosin V

binds vesicular cargo to transport it along actin filaments

4

domains of myosins

head

neck

tail

5

how to dissolve a myosin thick filament

solution of ATP and high salt

6

myosin II domains

2 heads and long tail connected by a flexible neck

tails intertwine and heads close together

7

myosin II has what type of activity

ATP hydrolysis (ATPase) in the S1 fragment

S1 also has F-actin binding site

8

all myosins have ___-_______ ATPase activity

actin-activated ATPase activity

9

sliding-filament assay

myosin attached to glass slide

actin filaments stained with phalloidin and ATP added

myosin heads walk toward + end, so looks like - end movement leads

10

tail domain

tailored to bind specific cargo

11

which domains of myosins are responsible for motor activity

head and neck (S1)

12

all myosin head domains convert what

ATP hydrolysis into mechanical work

13

myosin II assembles into _____ filaments

bipolar filaments

opposite orientations in each half so theres a cluster of head domains at each end

14

does myosin II have a short or long neck

short

15

myosin I

single headed

many functions

ex. connect actin filaments to membranes, endocytosis

16

myosin V domains

two heads and a long neck

tails dimerize

17

the length of the neck region affects the rate of myosin __________

movement

18

myosins move toward which end of the actin filament, except 1 myosin which moves toward the other end

+ end

myosin VI moves toward the - end

19

membrane-associated actin has their + end toward what?

the membrane

20

function of multinucleated skeletal muscle

produce gene products all along the cell

21

myosin heads do what along actin filaments

slide/"walk"

22

the hydrolysis of a single ATP molecule is coupled to each _____ taken by a myosin molecule along an actin filament

step

23

process of ATP-driven myosin movement along actin filaments

without ATP, the head is attached to F-actin

ATP binds the head, which releases the filament and hydrolyzes ATP --> ADP + Pi causing rocking

the myosin head binds actin

release of Pi is coupled to moving the actin filament forward (left) "power stroke"

ADP is released

24

the neck acts as a _____ point

pivot point

25

the myosin step size is proportional to what

neck length

tested by manipulating the genes for neck length (altered step size) and optical trap

26

step length of myosin II compared to myosin V

myosin V step length is 10x longer b/c of a very long neck (like a tether)

27

optical trap of myosin II

myosin on beads interacts with an actin filament held between 2 optical traps

when ATP is added, the myosin pulls the actin and a computer records the distance

28

what did the optical trap of myosin II show

that myosin II binds, moves, and releases the actin

it doesn't bind continuously

29

processive movement

myosin V takes sequential steps without releasing from actin

one head is always in contact with the actin

30

does myosin V walk hand over hand on an actin filament?

yes

31

can myosin V transport organelles?

yes

32

do microtubules have classes that move in opposite directions?

yes

33

what do the tail regions of myosins determine

what kind of cargo it carries

34

myosin ____ filaments and actin _____ filaments in skeletal muscle slide past one another during _______

myosin thick, actin thin, contraction

35

skeletal muscle fiber properties

long and multinucleated

striated

sarcomeres

36

smooth muscle fiber properties

no sarcomeres

mononucleate

non-striated

37

sarcomere

arrangement of actin/myosin

shortens by 70% during contraction

38

thick filaments are composed of what

myosin II bipolar filaments

move toward Z disk where + ends are, causing contraction of the muscle

39

skeletal muscle is structured by ________ and ________ proteins

stabilizing, scaffolding

actin capped by CapZ on the + end, and tropomodulin on the - end

nebulin goes from Z disk to tropomodulin (where it binds)

tintin is elastic and prevents overstretching

40

skeletal muscle contraction is initiated by an increase in cytosolic __

Ca2+

41

in skeletal muscle, a low cytosolic Ca2+ level is maintained by...

an ATPase that pumps Ca from the cytosol and into the sarcoplasmic reticulum

42

an action potential opens what in skeletal muscle

voltage-gated Ca channels in the SR membrane to raise cytosolic Ca concentration and induce muscle contraction

43

what effect does Ca have on skeletal muscle (thin-filament regulation)

changes tropomyosin and troponin which normally block myosin binding

allows myosin-actin interactions and therefore contraction

44

contractile bundle

bundles composed of actin and myosin that are found in nonmuscle cells

less organized than skeletal muscle fibers

45

in epithelial cells, contractile bundles are found as an ______ _____

adherens belt

46

3 types of contractile bundle

adherens belt - epithelium

stress fibers -ECM

contractile ring - cell division

47

skeletal muscle contraction is regulated by the ________-_______ complex bound to thin actin filaments

tropomyosin-troponin complex

switches between contraction inducing state in the presence of Ca, and the relaxed state without Ca

48

how is smooth muscle contraction regulated

cycling of myosin II in response to extracellular signaling molecules

phosphorylation/dephosphorylation of myosin regulatory light chain by myosin LC kinase (thick-filament regulation)

49

myosin V bound vesicles are carried along _____ filaments

actin

50

myosin V in budding yeast

carries secretory vesicles along actin filaments into the bud

distributes organelles

51

myosin V in giant green algae

cytoplasmic streaming

myosin V carries ER, which also moves cytoplasm

52

cell migration results from what

coordinated motions generated in different parts of the cell integrated with an endocytic cycle

53

how is cell migration initiated

formation of a large membrane protrustion at the leading edge of the cell - lamellipodium

54

cell migration of a fibroblast

membrane extension occurs at the leading edge where the network of actin filaments is nucleated by Arp2/3 (forms lamellipodium)

some lamellipodia anchor to the substratum via focal adhesions

the cell body is translocated forward by myosin II cortical contraction at rear of cell

focal adhesions at the back of the cell are broken and integrins recycled by endocytosis

freed tail snaps forward

55

the cell-adhesion molecules that mediate most cell-matrix interactions are membrane proteins called ______

integrins

external domain binds ECM (fibronectin and collagen)

cytosolic domain links them to the actin cytoskeleton

56

2 importances of focal adhesion attachment

prevents leading lamella from retracting

attaches cell to the substratum, allowing for forward movement

57

what 3 small GTP-binding proteins control actin organization

Rho

Rac

Cdc42

58

what do growth factors like epidermal growth factor and platelet-derived growth factor do

bind cell surface receptors and stimulate cells to move and then divide

ex. in a wound, platelets become active and secrete PDGF to attract fibroplasts and epithelial cells to the wound

59

what effect does dominant negative Rac have on wound healing

wound fails to close b/c Rac is needed to activate the Arp2/3 complex to form a lamellipodium

60

Cdc42 is critical for regulating ________ of cells

polarity

dominant negative results in formation of leading edge, but movement in random directions

61

migrating cells are steered by _______ molecules

chemotactic

ex. WBC are guided toward an infection by a tripeptide secreted by bacterial cells

62

common mechanism of chemotaxis

binding cell surface receptors

activate intracellular signaling pathways

remodel cytoskeleton through activation or inhibition of actin binding proteins

63

chemotaxis and amoebas

when stressed, these amoebas secrete cAMP which causes them to move toward each other

they them form a slug and make starvation-resistant spores

64

membrane recycling in cell migration

membrane needed to form lamellipodia is provided from internalization of adhesion molecules (including integrins) from old focal attachments to front of cell

65

dominant active protein

mutant small GTPase locked in the active state

66

dominant active Cdc42

appearance of filopodia through Arp2/3 activation via the NPF WASp

67

dominant active Rac

membrane ruffles/lamellipodium

68

dominant-active Rho

stress fibers that contract

69

general model of how cell migration is controlled via Rac, Rho, Cdc42

Cdc42 orients cell

oriented cell has high Rac activity in front to form lamellipodium

Rho activity is high in the rear to assemble contractile structures and activate myosin II