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MSK-1 > Contractile Proteins > Flashcards

Contractile Proteins Flashcards

1
Q

What are the 2 general types of actin structures?

A

actin bundles = parallel arrays, filaments have same polarity
actin networks = orthogonal arrays, mesh

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2
Q

What type of actin structure supports projections of the PM (microvilli)?

A

closely spaced actin filaments in parallel

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3
Q

What characterizes actin-bundling proteins?

A

cross-link F-actin w/ at least 2 actin-binding sites

size and shape of protein determines how actin associates (loose or tight)

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4
Q

What is fimbrin?

A

actin-bundling protein

holds 2 parallel filaments close together

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5
Q

What are contractile bundles?

A

loose bundles of actin filaments

give room for myosin to associate w/ actin

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6
Q

What is actinin

A

cross-linking protein for actin in loose bundles

binds as a dimer

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7
Q

What is filamin?

A

actin-bundling protein that holds actin in networks - can be 3D
binds as dimer
actin binding domains on opposite ends of dimer

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8
Q

What is spectrin?

A

tetramer that associates with actin in erythrocytes –> interacts w/ membrane proteins via ankyrin and protein 4.1

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9
Q

What is hereditary spherocytosis?

A

mutation in cytoskeleton proteins in RBCs (spectrin, ankyrin, 4.1) –> defective anchor pts –> membrane peels off and cell becomes spherical –> anemia

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10
Q

What are pseudopodia?

A

actin filaments cross-linked in 3D network –> phagocytosis

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11
Q

What are lamellipodia?

A

broad, sheet like extensions at leading edge of cell

made of network of actin filaments

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12
Q

What are filopodia?

A

Thin projections of PM supported by actin bundles

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13
Q

What characterizes the myosin superfamily?

A

all motor proteins
20 diff types
all move along actin via ATP hydrolysis

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14
Q

What characterizes myosin II?

A

in skeletal muscle
bipolar filaments
tails associate to form shaft
heads exposed

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15
Q

What are the 3 major domains of myosin?

A

Head
neck
tail

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16
Q

What is on the head of myosin?

A

actin binding sites
ATP binding sites
ATPase activity

17
Q

What is on the neck of myosin?

A

flexible

binds myosin light chain peptides

18
Q

What is on the tail of myosin?

A

intertwine to bring head regions close together

bind membrane/organelles

19
Q

What is type I myosin used for?

What is its step size

A

membrane association, endocytosis

10-14 nm

20
Q

What is type V myosin used for?

What is its step size?

A 
organelle transport
36 nm (largest)
21
Q

What is the basic mechanism of myosin moving along actin?

A

w/out ATP, myosin bound to actin –> bind ATP –> conformational change –> release actin = head cocked –> binds actin and release ATP –> power stroke = movement

22
Q

How does the size of neck of myosin relate to rate of movement along actin?

A

longer neck domain –> increased velosity

23
Q

What is the step size of myosin II?

A

8 nm (smallest = shortest neck)

24
Q

What end of actin does myosin move toward?

A

plus end of actin

25
Q

What end of actin is attached to the z disk?

What end of actin is closer to the m band?

A

+ end on z disk

- end at M band

26
Q

How are actin and myosin arranged in smooth muscle?

A

loosely arranged around periphery, held in place by protein dense bodies

27
Q

In smooth and non-muscle cells, what is myosin’s “relaxed” state?

A

folded and inactive

when there is low calcium

28
Q

In a smooth or non-muscle cell, what does an increase in calcium trigger?

A

CaM + MLC kinase to become active –> myosin unfolds and becomes active –> contraction myosin filament assembled

29
Q

what is the contractile ring?

A

what splits cells in cytokinesis

made of bundles of f-actin and myosin II

30
Q

How is vesicular transport accomplished?

A

myosin V is folded and inactive –> binds cargo –> straight and active –> carries vesicle through cell by moving along actin

31
Q

At what end of actin is there growth?

A

plus end

minues end = shrinkage

32
Q

What is important w/ focal adhesions in cell migration?

A

actin must pull adhesion off basement membrane to move cell

33
Q

What is duchene muscular dystrophy caused by?

A

x-linked recessive mutation of dystrophin gene

out of frame mutation

34
Q

What is becker muscular dystrophy? what is it caused by?

A

milder form of duchene

x-linked recessive, in-frame mutation of dystrophin gene

35
Q

What is the dystrophin protein?

A

rod-like protein that connects cytoskeleton to basal lamina and stabilize membrane
helps stabilize cell during muscle contraction; w/out it –> damage to muscles

36
Q

What is special about the dystrophin gene?

A

largest human gene known

MSK-1 (28 decks)

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