Lecture 17: Contractile Protiens Flashcards Preview

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

Flashcards in Lecture 17: Contractile Protiens Deck (40)
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1

Actin

What does this cytoskeletal protein determine?

  • Shape of the Cell
  • Cell Locomotion
  • Pinching of One Cell into two
    • Mitosis

2

Myosin

What is this cytoskeletal protein functions?

  • Use ATP to move organelles along filaments
  • Use ATP to move filaments on proteins

3

On which end of actin do we typically see growth?

The plus end

4

In G Actin, where can you find ATP?

In the ATP cleft, which faces the minus end

5

How does actin assemble into a filament?

  • 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 

6

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

When is equilibrium reached between the two?

  • 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

7

Where can you find actin filaments?

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

8

What determines the nature of the association of actin filaments?

How is cross linking achieved in F-actin?

The size and shape of the actin binding proteins

 

Acessory Proteins

9

What is the basic organization of actin parallel arrays?

What monomer binds the parralel arrays?

  • 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

10

Where in the cell can you find actin parallel bundles?

What do they do?

Location

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

Functions

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

11

Where do you see ATPase activity in Myosin?

In the Head region

12

What is a contractile ring made of?

Actin and Myosin II

13

What is the function of Myosin VI?

Moving vesicles towards the negative end of actin.

14

What actin bundling protein is present in contractile bundles?

 

Is this a tight or loose bundle?

Alpha-Actinin

 

Loose

15

Which end of actin does myosin move towards?

The plus end

16

What enzyme in smooth muscle activates myosin?

Myosin Light Chain Kinase

17

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

Why?

Fimbrin

 

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

18

What does the Dystrophen Gene do?

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

For Filamin:

Where are its actin binding domains located?

At the farthest ends of a dimerized structure

20

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

The side attached to the Z Disc

21

What is the function of Myosin I?

Assists with endocytosis

22

What causes a myosin "power stroke?"

Release of Pi

23

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

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

24

Which myosin might you find associated with a membrane?

Myosin I

25

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

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

26

What is the function of Myosin V?

Organelle and Vescicle transport along the actin cytoskeleton.

27

What is filamin?

 

What is its function?

Actin binding protein

 

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

28

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

Orthogonal Arrays

29

What -podia are commonly associated with phagocytosis?

Pseudopodia

30

Erythrocytes contain spectrin:

What does it do?

Forms the actin network that makes up the cortical cytoskeleton