Cytoskeleton 2

Question 1

What are features of the cytoskeleton?

Answer 1

Build from protein subuntis, nucleation is the first step in formation, polymerization creates polarity, nucleotide hydrolysis results in treadmilling, catastrphoe and rescue.

Question 2

How does listeria work?

Answer 2

It utilizes ARP2/3 complex which binds with ActA found on the bacterium. The bacteria can then utilize the actin found within the enterocytes to create a comet tail which propels the bacteria through the cell equivalent to the speed of a nuclear submarine destroying organelles in its path.

Question 3

What are the symptoms of Listeria?

Answer 3

headache stiff neck confusion loss of balance convulsions and fever and muscle aches. Pregnant women are 10x more at risk.

Question 4

What are the three types of actin accessory proteins?

Answer 4

1. Affect subunits
2. Affect filaments
3. Affect bundling cross linking etc..

Question 5

What is the ARP complex and what category of accessory protein is it?`

Answer 5

ARP complex affects subunits. It nucleates assembly of actin monomers causing branching of chains and remains associated with the minus end- growth occurs at the plus end. BYPASS RLS.
Requires an activating factor for ARP2/3.

Question 6

What is Formin and what category is it?

Answer 6

Formin nucleates actin subunits forming unbranched straight chains, it remains associated with the plus end.

Question 7

What is thymosin and what category is it under?

Answer 7

Thymosin binds to actin subunits preventing assembly but creating a soluble pool of actin monomers.

Question 8

What is Profillin and what category is it under?

Answer 8

Profillin binds to actin subunits speeding up elongation.

Question 9

What protein stops ARP 2/3 complex and dissassembles branched actin?

Answer 9

Cofillin

Question 10

What is tropomodulin?

Answer 10

Affects actin filaments. Preventws assembly and dissassembly at the minus end. Stabilizes seen in muscle!

Question 11

What is tropomyosin?

Answer 11

Stabilization protein that affects actin filaments. it prevents actin filamnt from interacting with other proteins-Key in erythrocyte cytoskeleton.

Question 12

What is cofillin?

Answer 12

Disassembly of actin filaments. Accelerates dissassembly binds to free subunits and filament causing twisting that weakens the bonds making it easily broke.

Question 13

What are the bundling proteins?

Answer 13

alpha actinin and fimbrin which cross link actin filaments into parallel arrays.

Question 14

What are the gel forming proteins?

Answer 14

Filamin. Holds two actin filaments together at a larage angle creating a loose meshwork.

Question 15

Differentiate between alpha actinin and fimbrin?

Answer 15

Fimbrin cross links into tight bundles excluding myosin II while alpha actinin corss links into loose bundles allowing myosin II to enter.

Question 16

What is the significance of filamin?

Answer 16

Helps cells crawl across solid surface allowing membrane projections to extend out.

Question 17

Spectrin?

Answer 17

Found in the erythrocyte cytoskeleton attaches it to the membrane. Gives the CS of RBC stability and durability. Disease can result in HS.

Question 18

Microtubule accessory proteins categories?

Answer 18

1. Tubulin Dimers
2. Microtubules
3. Filament cross linking

Question 19

What is gamma turc?

Answer 19

Affects tubulin dimers, nucleates assemblby and remains associated with the minus end.
Responsible for the nucleation of microtubule growth.
MT are nucleated at centrosome at the minus end with the plus end sticking out.
Gamma Turc is attached to the centrosome

Question 20

What does MAPs do?

Answer 20

Affect Microtubules. Stabilizes MT against disassembly they bind along side of microtubules which inhibits the switch from growth to shrinkage. (Catastrophe is suppressed and growth is enhanced) Contains two domains.

Question 21

What is XMAP215?

Answer 21

Microtubule associated protien that stablizes the plus ends and accelerates assembly. Inhinbits switch from growing to shrinking suppressing catastrophe.

Question 22

What is kinesin?

Answer 22

Microtubule associated protien that enhances catastrophe at the plus end. Lowers activation energy for subunibts to be pulled apart.

Question 23

What is Tau?

Answer 23

Filament cross linking protein that binds at the N and C terminal, similar to MAP but it loops and forms closer tightly packed bundles.

Question 24

What is MAP2?

Answer 24

Filament bundling and cross linking protein that has a long projecting domain widely spaced microtubules.

Question 25

What are the two major groups of motor protiens?

Answer 25

Kinesin and Dyneins

Question 26

Describe Kinesin.

Answer 26

Uses ATP to walk along microtubule towards the PLUS end, motor domain is at the N terminus of Heavy chain.
Binding site for membrane enclosed organelle is carried in the tail.

Question 27

Describe Dynein.

Answer 27

Largest and fastest motor protein, composed of 2-3 heavy chains, walks towards MINUS end.

Question 28

What are the two major branches of Dynein protein

?

Answer 28

Cytoplasmic dyneins for vesicle trafficking localiztion of golgi
Axonemal Dynein: specialized for rapid sliding movements that beat cilia and flagella

Question 29

What are short term cytoskeletal structures?

Answer 29

Mitotic spinkdle and those that assist with crawling across solid surface

Question 30

What type of movement is responsible for most cancer invasions?

Answer 30

Crawling into lymph vessels or blood

Question 31

Microtubules are primarily nucleated at the _____ and this is mediated by ______.

Answer 31

Centrosome, Gamma Tubulin

Question 32

Actin filaments are nucleated near _____ and mediated by ____ and ____.

Answer 32

Plasma membrane
ARP complex
Formin

Question 33

Motor proteins use energy of ____ to move along ____ or _____.

Answer 33

ATP hydrolysis
Microtubule
Actin filaments

Question 34

Motor proteins mediate transport of cargo along ____.

Answer 34

Microtubules