Lecture 16 - The Cytoskeleton 2

Question 1

What effect does kinesin-13 have on microtubules?

Answer 1

-separates protofilaments on free end facilitating depolymerization

Question 2

What effect does spectrin have on actin?

Answer 2

• connects actin filaments to cell membrane

- responsible for durability ad stability of RBCs

Question 3

What effect do MAPs have on microtubules?

Answer 3

• bind the side of microtubules
• stabilizes microtubules preventing disassembly
• suppresses catastrophe and enhances growth

Question 4

What effect does the ARP complex have on actin?

Answer 4

• consists of Arp2, Arp3, and activating factor
• Arp2 and Arp3 are very similar to actin
• branched growth
• activating factor causes conformation change to mimic plus end of actin allowing polymerization
• skips nucleation; allowing rapid growth
• responsible for the behavior of Listeria

Question 5

What effect does filamin have on actin?

Answer 5

• links two actin filaments together in a right angle
• forms a gel-like network
• used to hold cell membrane projections
• used in cell crawling

Question 6

What is the general structure of a cytoskeleton motor protein?

Answer 6

Motor domain (head):

• determines direction of movement
• ATPase function

Tail:
-determines cargo bound

Question 7

What proteins is responsible for propelling Listeria?

Answer 7

• ARP complex

- branching actin polymerization propels the bacteria

Question 8

What effect does tropomodulin have on actin?

Answer 8

• binds minus end of actin filaments
• prevents disassembly
• stabilizes long living filaments

Question 9

What effect do capping proteins have on actin?

Answer 9

• bind plus end preventing polymerization and depolymerization
• stabilizes filament

Question 10

What affect does the ERM family have on actin?

Answer 10

-mediates attachment of actin filaments to the plasma membrane via transmembrane proteins

Question 11

What effect does TIPS have on microtubules?

Answer 11

-associates with plus end and links to structures such as membranes

Question 12

Dysfunction of what actin binding protein results in anemia?

Answer 12

• spectrin which is used in binding actin to cell membrane

- spectrin is responsible for the flexibility and durability of RBCs

Question 13

What effect does stathmin have on microtubules?

Answer 13

-binds dimers and prevents assembly

Question 14

What effect does α-actinin have on actin?

Answer 14

• cross links filaments into loose bundles

- allows binding of myosin II

Question 15

What effect does fimbrin have on actin?

Answer 15

• cross links filaments into tight bundles

- does not allow for myosin II binding

Question 16

What is Listeria and what is special about how it uses host cells?

Answer 16

• pathogenic bacteria

- it recruits cellular actin and accessory proteins to propel it

Question 17

What effect does γ-TuRC have on microtubules?

Answer 17

• γ-tubulin ring complex
• responsible for nucleation of microtubules
• found in microtubule-organizing center (MTOC)/centrosome

Question 18

What effect does formin have on actin?

Answer 18

• dimeric protein associated with plus end
• binds monomers and facilitates linear polymerization

Helps in FORMINg actin polymers

Question 19

What effect does plectin have on microtubules?

Answer 19

-cross links microtubules to intermediate filaments

Question 20

What effect does Tau have on microtubules?

Answer 20

• binds microtubules at both the N- and C- terminus
• forms short projecting loop
• closely packed microtubule bundle

Question 21

What protein is responsible for depolymerization of Listeria comet trails?

Answer 21

-cofilin

Question 22

What effect does cofilin have on actin?

Answer 22

• binds actin filaments and twists them facilitating disassembly
• also called “acting depolymerizing factor”

Question 23

What effect does Katanin have on microtubules?

Answer 23

• severs microtubules

- comes from the Japanese work for “sword”

Question 24

What effect does XMAP215 have on microtubules?

Answer 24

• xenophobia microtubule-associated protein (215 kDa)
• stabilizes free end of microtubules
• suppresses catastrophe and enhances growth

Question 25

What effect does tropomyosin have on actin?

Answer 25

• binds actin filaments preventing binding of other accessory proteins
• stabilizing

Question 26

What effect does thymosin have on actin?

Answer 26

• binds actin monomers preventing polymerization

- “stores” monomers so they are available for polymerization later

Question 27

What effect does gelsolin have on actin?

Answer 27

• severs actin filament and binds to plus end
• creates smaller filaments
• can promote polymerization or depolymerization

Question 28

What are the different categories of cytoskeletal motor proteins and what differentiates them?

Answer 28

Kinesin:
-movement in the plus end

Dynein:
-movement towards the minus end

Question 29

What effect does profilin have on actin?

Answer 29

• binds actin monomers exposing binding sites

- facilitates polymerization

Question 30

What effect does MAP2 have on microtubules?

Answer 30

• binds microtubules with long protruding domain with additional microtubule binding domain
• widely spaced microtubules