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Contractile Proteins Flashcards

1
Q

What are the main cytoskeletal proteins?

A

Actin, actin binding proteins, and myosin

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2
Q

What determines the shape of the cell, its locomotion, and its ability to divide into two?

A

actin and actin binding proteins

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3
Q

What is the molecular machine that converts biochemical energy from ATP hydrolysis to mechanical energy that can move filaments on proteins or move organelles along filaments?

A

Myosin

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4
Q

What is each actin subunit referred to as?

A

g-actin

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5
Q

the polymerization of G actin forms what?

A

F actin

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6
Q

Why is the polarity of actin filaments important?

A

for their assembly and in establishing a unique direction of myosin movement relative to actin

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7
Q

the lag phase is also known as?

A

nucleation

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8
Q

the growth phase is also known as?

A

elongation

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9
Q

the equilibrium phase is also known as?

A

steady state

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10
Q

For a new actin filament to form, what is required?

A

subunits must assemble into an initial aggregate, where the nucleus is made up of 3 actin monomers

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11
Q

Process where subunits assemble into an initial aggregate, where the nucleus is made up of 3 actin monomers

A

nucleation

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12
Q

What do actin monomers have bound to them?

A

ATP

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13
Q

When actin filaments are assembled, what happens to the bound ATP?

A

it is hydrolyzed to ADP and Pi

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14
Q

Critical concentration

A

monomers and filaments of actin are in apparent equilibrium

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15
Q

Where are actin filaments particularly abundant?

A

beneath the plasma membrane

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16
Q

How is cross-linking of F-actin achieved?

A

accessory proteins

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17
Q

How is the nature of association of actin filaments determined?

A

by the size and shape of cross-linking proteins

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18
Q

What are the two general types of structures that actin filaments are assembled into?

A

Actin bundles and actin networks

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19
Q

cross-linked into closely packed parallel rays

A

actin bundles

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20
Q

loosely cross-linked in orthogonal arrays that form three-dimensional meshwork with more flexible gel-like properties

A

actin networks

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21
Q

Which general structure has the polarity of actin filaments different?

A

actin networks

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22
Q

what are parallel bundles made up of?

A

actin filaments and fimbrin monomer

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23
Q

what are contractile bundles made up of?

A

actin filaments and alpha-actin

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24
Q

Which actin bundle allows myosin II to enter the bundle?

A

contractile bundle

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25
Which actin bundle supports projections of plasma membrane (e.g. microvilli)
parallel bundles
26
How many actin binding domains does fibrin have?
2
27
How does alpha-actinin bind?
as a dimer
28
What is an example of contractile bundles?
contractile ring used in mitosis
29
What is an example of parallel bundles?
microvilli.
30
What are two examples of actin bundles?
parallel bundles and contractile bundles
31
What is the large actin binding protein that holds actin filaments together in networks?
filamin
32
Which structure of actin filaments creates a #D meshwork?
actin-networks
33
Erythrocytes contain what actin binding protein?
spectrin
34
How does the spectrin-actin network interact with membrane proteins?
via interactions with ankyrin and protein 4.1
35
How is hereditary spherocytosis caused?
caused by mutations in erythrocyte cortical cytoskeleton proteins (Spectrin, Ankyrin, and protein 4.1)
36
How do myosin motor proteins move along actin filaments?
via ATP hydrolysis
37
What part of the myosin contains the actin binding and ATP binding sites?
the head
38
What part of the myosin is considered the flexible region and binds myosin light chain peptides?
the neck
39
what part of the myosin binds membrane/organelles?
the tail
40
Which myosin type has one heavy chain with a head domain and a neck domain?
Myosin I
41
Which myosin head has two heavy chains-each with head and neck domain that binds two different light chains?
Myosin II
42
Which myosin head has two heavy chains and six light chains per neck?
Myosin V
43
Which myosin head is used in muscle contraction?
Myosin II
44
Which Myosin head is used in transport?
Myosin V
45
What causes the released myosin head to rotate into "cocked" state?
hydrolysis of ATP to ADP and Pi
46
What causes the "powerstroke"
release of Pi and the elastic energy straightens myosin and moves the actin filament left
47
Myosin will remain in the "cocked" state until when?
until it binds to actin filament
48
What does the binding of actin cause the myosin to do?
release Pi, which will cause the power stroke
49
The head remains tightly bound to the actin filament until when?
ADP is released, and fresh ATP is bound by the head
50
What is the velocity of the powerstroke dependent on?
the length of the neck
51
A longer myosin neck domain will cause?
An increase in the rate of movement
52
What are thick filaments made up of?
6 myosin polypeptide chains
53
When muscle fiber is at rest, what is the state of the myosin binding sites on actin?
they are covered by tropomyosin so that actin and myosin cannot interact
54
How is the sarcomere structure stabilized?
by capping and scaffolding proteins
55
How are actin filaments stabilized on their + ends?
by CapZ
56
How are actin filaments stabilized on their - ends?
by tropmodulin
57
a giant protein that extends along the actin filament all the way from the Z disk to tropomodulin
Nebulin
58
Where does nebulin bind?
to tropomodulin
59
What determines the length of the thin filaments?
the length of nebulin
60
Has its head associated with the Z disk and extends to the middle of the thick filament
titin
61
What is the purpose of titin?
its an elastic molecule that holds the thick filaments in the middle of the sarcomere and prevents overstretching
62
What do titan mutations cause?
cardiomyopathies
63
Under resting conditions, is the cytosolic calcium level high or low?
low
64
What is the SERCA
Sarcoplasmic reticulum Ca2+ ATPase
65
What does SERCA activity establish?
a reservoir of Ca2+ in the sarcoplasmic reticulum
66
What is calcium induced calcium release?
depolarization stimulates the opening of voltage-gated Ca2+ channels in the sarcoplasmic reticulum. This brings in extracellular Ca2+, which then causes release of Ca2+ for the SR
67
What happens after Ca2+ is released from the SR?
there is an elevation of cytosolic Ca2+ concentration in the myofibrils
68
Elevated Ca2+ concentration in the myofibrils causes what?
conformation change in tropomyosin and troponin
69
What activates contraction of smooth muscle?
phosphorylation of the myosin regulatory light chain
70
A contractile ring is formed by what?
Bundles of F actin and Myosin II
71
part of a protein complex that links the cytoskeleton of muscle fibers to the surrounding connective tissue (basal lamina)
dystrophin
72
2 functions of dystrophin?
Shock absorber and stabilizes the sarcolemma
73
Loss of dystrophin would lead to what?
duchenne's muscular dystrophy
74
What type of disorder is duchenne's muscular dystrophy?
x-linked recessive
75
who are DMD carriers?
females
76
what is the milder form of DMD?
Becker muscular dystrophy
77
2/3 of mutations in dystrophin result in what?
large internal deletions
78
out-of-frame mutants?
DMD
79
in frame mutants leads to what?
BMD

MSK Final (16 decks)

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