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04. MSK Exam 2 Final > Lecture 17: Contractile Protiens > Flashcards

Lecture 17: Contractile Protiens Flashcards

1
Q

Actin

What does this cytoskeletal protein determine?

A
  • Shape of the Cell
  • Cell Locomotion
  • Pinching of One Cell into two
    • Mitosis
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2
Q

Myosin

What is this cytoskeletal protein functions?

A
  • Use ATP to move organelles along filaments
  • Use ATP to move filaments on proteins
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3
Q

On which end of actin do we typically see growth?

A

The plus end

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4
Q

In G Actin, where can you find ATP?

A

In the ATP cleft, which faces the minus end

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5
Q

How does actin assemble into a filament?

A
  • Stage 1: Nucleation (Lag Phase)
    • ​Small acting oligomers must first form an aggregate of 3 actin monomers
    • Each aggregate must be stabilized
  • Stage 2: Elongation (Growth Phase)
    • ​Multiple subunits contract and elongate rapidly
    • If actin is bound to ATP, polymerization happens much more quickly
  • Stage 3: Steady State (Equilibrium)
    • ​Depends on concentration of free actin
    • Rate of polymerization = Rate of depolymerization
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6
Q

What is the difference between the rate of subunit association and dissociation?

When is equilibrium reached between the two?

A
  • Subunit association: Proportional to concentration of free monomers
    • C x kon
  • Subunit dissociation: Independent of monomer concentration
  • Equilibrium: Reached at critical concentration of monomers
    • koff = Cc x kon
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7
Q

Where can you find actin filaments?

A
  • Beneath plasma membrane
  • Mechanical Support
  • Determining Cell Shape
  • Movement of Cell Surface
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8
Q

What determines the nature of the association of actin filaments?

How is cross linking achieved in F-actin?

A

The size and shape of the actin binding proteins

Acessory Proteins

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9
Q

What is the basic organization of actin parallel arrays?

What monomer binds the parralel arrays?

A
  • Actin fibers are crosslinked together with all of their plus and minus ends on the same side.
  • Parallel fibers are very close and doesn’t allow Myosin II from entering the bundle
  • Fimbrin binds actin
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10
Q

Where in the cell can you find actin parallel bundles?

What do they do?

A

Location

  • Projections of Plasma Membranes
  • Microvilli
  • Cell Cortex
  • Adherens belt

Functions

  • Placement of receptors and channels
    • Facilitate signaling, transport, uptake of nutrients
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11
Q

Where do you see ATPase activity in Myosin?

A

In the Head region

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12
Q

What is a contractile ring made of?

A

Actin and Myosin II

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13
Q

What is the function of Myosin VI?

A

Moving vesicles towards the negative end of actin.

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14
Q

What actin bundling protein is present in contractile bundles?

Is this a tight or loose bundle?

A

Alpha-Actinin

Loose

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15
Q

Which end of actin does myosin move towards?

A

The plus end

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16
Q

What enzyme in smooth muscle activates myosin?

A

Myosin Light Chain Kinase

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17
Q

What actin bundling protein would you find cross linking the actin in a microvillus?

Why?

A

Fimbrin

Fimbrin holds actin fibers close together, which is more beneficial in a microvillus

18
Q

What does the Dystrophen Gene do?

A

Connects Cytoskeleton to the basal lamina, stabilizes the membrane, and in so doing, helps to relieve the stress of contraction by spreading the forces out.

19
Q

For Filamin:

Where are its actin binding domains located?

A

At the farthest ends of a dimerized structure

20
Q

In a sarcomere, which side of the actin would be the plus side?

A

The side attached to the Z Disc

21
Q

What is the function of Myosin I?

A

Assists with endocytosis

22
Q

What causes a myosin “power stroke?”

A

Release of Pi

23
Q

In a sarcomere which side of the actin would be the minus side?

A

The side farthest from the Z Disk (in the A Band)

24
Q

Which myosin might you find associated with a membrane?

A

Myosin I

25
Q

What do contractile bundles do to help a cell move forward?

A

They pull the plunger-like integrins off of the extracellular matrix so they don’t get stuck.

26
Q

What is the function of Myosin V?

A

Organelle and Vescicle transport along the actin cytoskeleton.

27
Q

What is filamin?

What is its function?

A

Actin binding protein

Creates three dimensional meshworks by binding to an actin binding domain on two different actin fibers.

28
Q

What is the organizational name for actin networks’ three dimensional meshworks?

A

Orthogonal Arrays

29
Q

What -podia are commonly associated with phagocytosis?

A

Pseudopodia

30
Q

Erythrocytes contain spectrin:

What does it do?

A

Forms the actin network that makes up the cortical cytoskeleton

31
Q

Where would we see an actin contractile bundle?

A

In muscles to assist in contraction

In the contractile ring of mitosis

32
Q

What is the only myosin that moves towards the negative end of actin?

A

Myosin VI

33
Q

Which myosin is typically associated with skeletal muscle?

A

Myosin II

34
Q

What fiber is an essential component of pseudopodia, filopodia, and lamellopodia?

A

Actin

35
Q

What is the heredity of Duchene’s Muscular Dystrophy?

A

X Linked Recessive

36
Q

What will a myosin with a longer neck have over a myosin with a shorter neck?

A

A Myosin with a longer neck will have a greater power stroke velocity (increased rate of movement)

(Keep in mind this is not referring to the length of the tail, but the light chain neck portion)

37
Q

What might be deficient in Hereditary Spherocytosis?

A

Cortical skeleton of the red blood cells

(More specifically, Spectrin, Ankryin, or Protein 4.1)

38
Q

Where might you find myosin light chain peptides?

A

In the Neck region

39
Q

What contributes to the prevention of myosin binding to actin in smooth muscle?

What enzyme causes this inhibitory state?

A

Folding of the myosin by the regulatory light chains in the neck

Myosin Light Chain Phosphatase

40
Q
A

04. MSK Exam 2 Final (24 decks)

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