Lecture 19- Actin Filaments Flashcards
What is the subunit of Actin Filament/ F-actin
Globular actin/ G-Actin
How do F-Actins assemble themselves?
Treadmilling
At (-) end they fall off and at (+) end is where they are added.
Difference of treadmilling in Actin and Dynamic instability in Microtubules
Treadmilling: (+) end grows and (-) shrinks
Dynamic instability: (+) end grows and shrinks
What stops treadmilling fron happening in cells?
= There are many ___-binding proteins
Actin
If you want to organize F-actin into structure, actin-binding proteins must bind in the _____
Middle
If you want actin filament to stop growing, the actin-binding proteins should bind at the ___- end
Plus end
If you want actin filaments to be smaller, actin-binding proteins should cut in the ____
Middle
If you want actin filament to grow, (grow longer and won’t shrink) actin-binding proteins should bind at the ___ end
Minus end
ARP Complex (Nucleating Protein)
Anchors the (-) end, allow the (+) end to griow longer and longer.
ARP Complexed can be free or attached to other F-actins.
Two ways ARP Complexes can grown an actin filament
- It can sit by itself and grow an actin filament
- It can connect to the side of an actin filament and grow another one in a new direction.
ARP Complex is both a nucleating protein and an acting-binding protein that can bind in the middle
True or False
TRUE
F-Actins can form 1D, 2D, or 3D structures
True or False
TRUE
Why is F-actin stability desirable?
Hint: intestine cells
Microvilli (which is an actin filament) increases the surface area of intestine cells.
Two important Actin-binding proteins that contribute to the stability of F-actin (both of them bind in the middle of actin filaments)
- Cross-linking proteins (Filamin)- organizes actin filaments into crosses to make up the cell cortex.
- Bundling proteins (Villin-in the microvilli) - holds actin together.
What are the three Actin-binding proteins and their function
- Nucleating- allow growth of F-actins
- cross-linking - holds F-actins into meshes to make up the cortex
- Bundling- holds F-actins into parallel bundles
Which of these is similar in function to gammaTuRC? (Nucleates MT formation)
A. G-Actin
B. ARP Complex
C. Filamen
D. Villin
ARP complex
What are actin filaments made of?
Made of G-actin that has been assembled into F-actin strands
How are actin filaments organized in immobile cells, for example intestinal epithelial cells?
Organizes actin filaments into crosses (Filamin) or bundle them (Villin)
How are actin filaments organized in cells that crawl, for example amoeba?
Make actin filaments in new random direction
If you were to use fluorescently labeled antibodies to determine the location of the gamma Tubulin in a human cell you would find it:
A. On the surface of the centrosome
B. Inside the centrosome
C. Along the length of each microtubule
D. At the tips of growing microtubules
E. At the tips of shrinking microtubules.
On the surface of the centrosome
