Cytoskeleton (IF and MT)

Question 1

Generic kinesin structure

Answer 1

motor (head) domain = contains ATP binding site + MT binding site, determines movement
neck = flexible region connecting motor domain to central stalk, determines direction

Question 2

Kinesin 1

Answer 2

~ globular bulbous region (motor domain) at one end of the molecule
~ region is enlarged when specific antibody present
Function: organelle transport

Question 3

Kinesin 5

Answer 3

~ two bulbous regions - one at each end of the molecule (bipolar kinesin)
~ tetramer (two dimers joined together by tails overlapping)
Function: involved with sliding MT overreach in mitotic spindle

Question 4

Dyneins

Answer 4

~ MT motor protein
~ move cargo towards -ve end of MT (retrograde)
~ linked to cargo by dynactin

Question 5

Dynein structure

Answer 5

~ dynactin binding domain
~ ATPase domain (x2)- circular with 6 sections
~ microtubule binding domain (one per ATPase) a.k.a. feet

Question 6

Dynactin

Answer 6

contains CapZ and dynamitin

Question 7

Multi-directional cargo

Answer 7

~ some cargos are able to move in both directions –> have kinesin and dynein but only one is active at a time
e.g. pigment granules + mitochondria

Question 8

What speed does kinesin travel at?

Answer 8

600nm per second = slow

Question 9

Axoneme

Answer 9

core of cilia and flagella
~ made of 9 outer MT doublets and a central pair (9 +2 arrangement)
~ each outer doublet = 1 13 protofilament and 1 10 protofilament
~ centraal doublet = 13 protofilaments
~ cell movement depends on axoneme bending

Question 10

Kinetochore MT

Answer 10

connect chromo. to spindle poles (kinetochore attachment site)

Question 11

What microtubules are in spindle?

Answer 11

Kinetochore MT = connect chromo. to spindle poles (kinetochore attachment site)
Polar MT = overlap and hold the poles together and regulate their distance
Astral MT = from spinal pole towards cell cortex, help to position the spindle

Question 12

Polar MT

Answer 12

overlap and hold the poles together and regulate their distance

Question 13

Intermediate filaments

Answer 13

protein subunits that make a strong rope-like polymers that provide mechanical support or cell adhesion
e.g. keratin + lamin

Question 14

IF structure

Answer 14

~ globular N-terminal and C-terminal domains connected by a central, helical core
~ the core = conserved among all IF, mediates dimer and tetramer formation

Question 15

Multi-IF structure

Answer 15

~ form protofilaments (out of tetramers)
~ 2 protofilaments form a protofibril
~ 4 protofirbil wind around each other = rope structure

Question 16

List the 5 IF classes

Answer 16

1. Acidic keratins = tissue strength and integrity
2. Basic keratins = “ “
3. Desmin+ = sarcomere organisation
4. Neurofilaments = axon organisation
5. Lamins = nuclear structure and organisation

Question 17

Mechanism of Kinesin bulbous head + ATP

Answer 17

1. forward motor binds beta-tubulin, releasing ADP
2. forward head binds ATP
3. conformational change in neck linker causes rear head to wing forward
4. new forward head releases ADP, trailing head hydrolyses ATP and releases Pi