Lecture 3- Microfilaments

Question 0

What makes up Microfilaments

Answer 0

Actin

Question 1

3 Structures of the Cytoskeleton

Answer 1

1) Microfilaments
2) Intermediate Filaments
3) Microtubules

Question 2

How do Actin filaments connect to the membrane

Answer 2

Via transmembrane proteins either directly or indirectly

Question 3

What is the structure of an Actin Filament

Answer 3

G-actin monomers bind together in a double-helical formation via ATP hydrolysis to form F-actin actin filaments.

Question 4

What are the 2 ends of an Actin Filament

Answer 4

Barbed end/Plus end/Polymerized end

Pointed end/Minus end/Depolymerized end

Question 5

Treadmilling

Answer 5

When F-actin is polymerized and depolymerized at the same rate, making an equilibrium of G-actin monomer concentration

Question 6

Actin-binding proteins (function)

Answer 6

Determine the “job/function” of the Actin filament

Question 7

Cytochalasin

Answer 7

Actin-binding protein that bind to barbed end and prohibit polymerization/elongation (made from fungi)

Question 8

Phalloidin

Answer 8

Actin-binding protein that prevents depolymerization (made from mushrooms)

Question 9

Latrunculins

Answer 9

Actin-binding protein that binds pointed end facilitating depolymerization of individual G-actin

Question 10

Spectrin

Answer 10

Actin-binding protein found in RBC’s that attaches cortical cytoskeleton to plasma membrane

Question 11

Dystrophin

Answer 11

Actin-binding protein (not in RBC’s) that attaches cortical cytoskeleton to plasma membrane

Question 12

Villin

Answer 12

Actin-binding protein that attaches F-actin filaments together within microvilli

Question 13

Fimbrin

Answer 13

Actin-binding protein that binds F-actin filaments together within microvilli

Question 14

Calmodulin

Answer 14

Actin-binding protein that binds F-actin filament to wall of microvilli

Question 15

Myosin I

Answer 15

Actin-binding protein that binds F-actin filament to wall of microvilli

Question 16

Alpha-actin

Answer 16

Actin-binding protein that binds F-actin filaments to integrins/plasma membrane (like catenins for caherins)

Question 17

Filamin

Answer 17

Actin-binding protein that links F-actin at wide angles and forms screen-like gels

Question 18

Thymosin

Answer 18

Actin-binding molecule that binds to G-actin monomer (containing ATP) and sequesters it until polymerization is needed

Question 19

Profilin

Answer 19

Actin-binding molecule that binds to G-actin and exchanges an ATP for the ADP…can sequester G-actin monomers sometimes

Question 20

Gelsolin

Answer 20

Actin-binding molecule that cuts and caps off a portion of the F-actin to prevent further polymerization and promote depolymerization (by Cofilin)

Question 21

Cofilin

Answer 21

Actin-binding molecule that depolymerizes cut off F-actin link into G-actin monomers (with ADP on them)

Question 22

Arp2/3

Answer 22

Actin-binding molecule that binds to existing F-actin filament causing branching to occur

Question 23

Actin Nucleation

Answer 23

The formation of a “nucleus” of 3 G-actin monomers via random collision that begins the formation of an F-actin filament