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MSK Final > Contractile Proteins > Flashcards

Contractile Proteins Flashcards

1
Q

McArdle disease

A

a deficiency in in the muscle form of glycogen phosphorylase

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2
Q

Patients with McArdle disease are unable to supply what to muscles?

A

Glucose

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3
Q

Patients with McArdle disease suffer what?

A

fatigue, severe muscle cramping, and muscle breakdown. Myoglobin occurs in urine during intense exercise. Patients tolerate disease by decreasing strenuous physical activity.

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4
Q

Where are liver and muscle glycogen phosphorylase genes located?

A

Liver and muscle isoforms of phosphorylase are products of separate genes located on chromosomes 14 and 11, respectively

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5
Q

Liver glycogen phosphorylase mutations cause:

A

Liver isoform mutations cause Hers disease (GSD VI)

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6
Q

Muscle glycogen phosphorylase mutations cause

A

Muscle isoform mutations cause McArdle syndrome (GSD V)

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7
Q

Both muscle and liver glycogen phosphorylase are activated by:

A

PhK (phosphorylase kinase)

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8
Q

Both muscle and liver glycogen phosphorylase are inactivated by:

A

ATP and Glucose 6-phosphate

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9
Q

Muscle glycogen phosphorylase is activated by:

A

PhK, AMP, Ca2+ calmodulin complex and G-actin, Ca2+

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10
Q

LIver glycogen phosphorylase is inactivated by:

A

free glucose. Is not affected by AMP

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11
Q

Brain glycogen phosphorylase lacks a phosphorylation site for what?

A

PhK, but is responsive to AMP

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12
Q

Ca2+ - calmodulin is further capable of activating what?

A

Phosphorylase - alpha

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13
Q

Phsophorylase - alpha does what?

A

Degrades glycogen to produce ultimately produce ATP

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14
Q

What is Dantrolene?

A

A muscle relaxant that binds to ryanodine receptors

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15
Q

What does Dantrolene prevent?

A

Mobilization of Ca2+ and subsequent activation of phosphorylase alpha

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16
Q

Dantrolene is used to treat what?

A

Malignant hyperthermia caused by anesthesia in susceptible patients

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17
Q

Malignant hyperthermia is enhanced by mutations in what two proteins?

A

Ryanodine receptors or L-type voltage-gated Ca2+ channels

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18
Q

What is malignant hyperthermia caused by?

A

Reabsorption of mobilized Ca2+, which requires larges amounts of ATP

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19
Q

Myosin is a superfamily consisting of:

A

class II, two-headed myosins that form filaments.

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20
Q

Myosin is found in:

A

striated muscle, smooth muscle and non-muscle cells

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21
Q

Myosin is described as a ______ protein

A

hexameric

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22
Q

Myosin consists of:

A

two myosin heavy chain (MyHC) subunits and two pairs of non-identical light chain subunits

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23
Q

Myosin globular head domain binds:

A

actin and ATP (required for motor activity)

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24
Q

Myosin rod domain is:

A

near alpha-coiled and assembles into thick filaments of sacromeres

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25
Q

MyHC isoforms

A

MyHC I, MyHC IIa, MyHCIIx

26
Q

MyHC I

A

slow, Type I muscle fibers and heart ventricles

27
Q

MyHC IIa

A

fast, Type IIa fibers

28
Q

MyHCIIx

A

fast, Type IIB fibers

29
Q

Dermatomyositis

A

disappearance of myosin and other proteins with thick filaments

30
Q

Dermatomyositis is frequently triggered by:

A

systemic corticosteroid hormone treatment, postsynaptic block of neuromuscular transmission and prolonged mechanical ventilation

31
Q

Dystrophin is a:

A

rod shaped cytoplasmic protein

32
Q

Dystrophin does what?

A

Connects cytoskeleton of a muscle fiber to the surrounding ECM through the cell membrane

33
Q

Dystrophin stabilizes what?

A

Stabilizes the sarcolemma against mechanical forces experience during muscle contraction or stretch – a molecular shock absorber

34
Q

Dystrophin is part of what complex?

A

costamere or dystrophin-associated protein complex

35
Q

Duchenne muscular dystrophy

A

X linked, recessive disorder with incidence of 1 in 3500 boys and leads to progressive muscle wasting

36
Q

Becker muscular dystrophy

A

milder than DMD with later onset

37
Q

Duchenne and Becker muscular dystrophy are both due to:

A

mutations in dystrophin gene which codes for dystrophin

38
Q

Becker muscular dystrophy is

A

in frame mutation - produces smaller dystrophin proteins

39
Q

Duchenne muscular dystrophy is

A

Out-of-frame and results in little to no dystrophin expression

40
Q

Desmin

A

muscle specific, type III intermediate filament that integrates the sarcolemma, Z disk and nuclear membrane in sarcomeres and regulates sarcomere architecture

41
Q

High Ca2+ levels cause ____ in skeletal muscle

A

Contraction

42
Q

Low Ca2+ levels cause ____ in skeletal muscle

A

relaxation

43
Q

Troponin is

A

a trimeric protein complex that plays role in muscle contraction and relaxation triggered by elevated or depressed levels of intracellular Ca2+.

44
Q

Subunits of troponin:

A

tropomysin-binding subunit (Tn-T), calcium-binding subunit (Tn-C) and the inhibitory subunit (Tn-I).

45
Q

Describe sequence of events following calcium binding to troponin

A

When calcium binds, the protein changes conformation, which is transmitted to tropomysin, which allows myosin to bind the actin filaments, enabling muscle contraction.

46
Q

Tn-I subunit comes in three isoforms

A

cTn-I: in cardiac muscle. Serum levels increase after myocardial infarction

sTn-I: in skeletal muscle (two isoforms of this)

47
Q

MLCK/calmodulin is what kind of protein

A

Myosin light-chain kinase is a serine/threonine specific protein kinase that phosphorylates the regulatory chain of myosin II

48
Q

MLCK/calmodulin is a muscle contraction alternative to troponin found in what kind of muscle

A

smooth muscle

49
Q

MLCK is activated via:

A

Calcium binding to calmodulin in smooth muscle

50
Q

Activated MLCK ______ myosin light chain causing a _______ change

A

phosphorylates/conformational

51
Q

Contraction in smooth muscle occurs following myosin _____ binding to the _____ filament

A

cross bridge/actin

52
Q

How is smooth muscle contraction terminated?

A

Only by dephosphorylating the myosin light chain (this is due to the induced conformational change)

53
Q

How many poles does the myosin assembly have?

A

Two - it is bipolar

54
Q

Myosin (head region) does what to ATP?

A

Hydrolyzes it

55
Q

What is the P-loop?

A

It is the location of the ATPase domain within the S1 region of the myosin globular head region

56
Q

Thin filaments are

A

Actin

57
Q

G-actin –> what?

A

F-actin

58
Q

Nebulin is

A

a 1mm long template for the length of actin polymerization

59
Q

Tropomyosin is

A

wrapped around actin filaments and blocks the myosin binding sites

60
Q

Titin is

A

involved in sarcomere organization. Balances the forces across sarcomere. Assists in passive elasticity and muscle signaling

61
Q

The myosin binding site is exposed by:

A

calcium binding troponin complex (at site C) and inducing movement of tropomyosin out of the fucking way

62
Q

Glycogen phosphorylase is an _____ enzyme

A

allosteric (for AMP)

MSK Final (7 decks)

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