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MSK II > Contractile Proteins > Flashcards

Contractile Proteins Flashcards

1
Q

which type of actin has polarity: globular or filamentous?

A

filamentous

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2
Q

actin bundles

A

cross-linked actin into closely packed parallel arrays

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3
Q

actin networks

A

loosely cross-linked actin into orthogonal arrays that form 3D meshworks with gel-like properties
- more flexible

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4
Q

actin-bundling proteins

A

small, ridged proteins that force the filaments to align closely with each other

  • cross-links actin
  • determines the nature of association of filaments
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5
Q

fimbrin

A

actin-bundling protein; binds to actin filaments as a monomer; holds two parallel filaments closely together
- ex: microvilli

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6
Q

contractile bundles of actin

A

loosely bundled actin

- ex: contractile ring used in mitosis

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7
Q

alpha-actinin

A

actin bundling protein; allows motor protein (myosin) to interact during contraction; binds as a dimer; filaments of actin are separated by a greater distance which allows myosin to interact during contraction

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8
Q

filamin

A

actin bundling protein; binds actin as a dimer; can create 3D meshwork

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9
Q

spectrin

A

actin binding protein in RBCs; forms actin network that forms a cortical cytoskeleton; this network interacts with membrane proteins via interactions with ankyrin, protein 4.1

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10
Q

hereditary spherocytosis

A

decrease flexibility and stability of RBCs; caused by mutations in the cortical cytoskeleton proteins in RBCs (spectrin, ankyrin, 4.1)
- Sx: jaundice, anemia, splenomegaly

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11
Q

pseudopodia

A

type of actin projection that is responsible for phagocytosis

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12
Q

lamellipodia

A

broad, sheet like extensions of actin at the leading edge of a moving cell

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13
Q

filopodia

A

thin projections of plasma membrane supported by actin bundles; formation and retraction of filopodia is based on regulated assembly and disassembly of actin filaments

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14
Q

what driving force allows myosin to move along actin filaments

A

ATP hydrolysis

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15
Q

head domain of myosin

- two parts

A

contains actin binding and ATP binding sites; ATPase activity

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16
Q

neck domain of myosin

A

the flexible region; binds myosin light chain peptides

17
Q

tail domain of myosin

A

intertwines to bring myosin head regions in close proximity; binds membranes and organelles

18
Q

skeletal muscle myosin I

  • neck size
  • function
A
  • 10-14 (small)

- interacting with membranes, endocytosis

19
Q

skeletal muscle myosin II

  • neck size
  • function
A
  • 8 nm (v small)

- skeletal muscle contraction

20
Q

skeletal muscle myosin V

  • neck size
  • function
A
  • 36 nm (v long)

- organelle transport

21
Q

how does rigor mortis occur

A

absence of ATP in the muscle –> myosin attaches to actin filaments and contracts and cannot relax

22
Q

what happens when ATP binds to myosin

A

a conformational change occurs causing release of actin; myosin then remains in “cocked state” –> binds to actin causing release of Pi (energy) –> “power stroke”

23
Q

“power stroke” of myosin bound to actin

A

release of P and i elastic energy which straightens myosin; moves actin filaments to the left

24
Q

as length of neck domain of myosin increases, ____

A

rate of movement increases

25
Q

what form is myosin in during low Ca2+ environements

A

folded

26
Q

what phosphorylates myosin

A

MLC (myosin light chain) kinase

27
Q

phosphorylation of myosin by MLC kinase causes ___

A

unfolding and activation of myosin

28
Q

what activates MLC kinase

A

calcium

29
Q

what dephosphorylates myosin

A

MLC (myosin light chain) phosphatase

30
Q

dephosphorylation of myosin causes

A

folding and relaxation of myosin (inactive)

31
Q

what causes the cleavage furrow in cytokinesis

A

myosin movement along actin filaments

32
Q

difference between myosin VI and myosin V in moving across filamentous actin

A

myosin VI moves towards the (-) end

myosin V moves towards the (+) end

33
Q

difference between dynein and kinesin in moving across filamentous actin

A

dynein moves toward (-) end

kinesin moves toward (+) end

34
Q

Duchenne Muscular Dystrophy

  • type of disorder
  • what is it
A
  • X-linked recessive

- progressive muscle wasting due to mutations within dystrophin gene

35
Q

in-frame mutations in the dystrophin gene cause

A

becker muscular dystrophy

36
Q

out of frame mutations in the dystrophin gene cause

A

duchenne muscular dystrophy

37
Q

function of dystrophin

A

connects cytoskeleton to basal lamina; stabilizes the membrane of muscle cells

MSK II (17 decks)

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