MAPs and ABPs

Question 1

Stathmin

Answer 1

MAP - inhibited during mitosis by phosphorylation

• normally binds to tubuulin and inhibits MT polymerisation
• increases likelihood of catastrophe

Question 2

phosphorylation of stathmin

Answer 2

inhibits interaction with tubular - so tubular can polymerise to form Mts

Question 3

how many molecules of tubular does stathmin bind

Answer 3

2 heterodimers

Question 4

stathmin over expression in cancer cells

Answer 4

cancer cells frequently over express stathmin - inc. rate of MT turnover - contribute to change in cell shop and associated with malignant transformation

Question 5

which protein is though to phosphorylate stathmin in the cell cycle

Answer 5

cdc2

Question 6

3 types of Mts in a cell undergoing mitosis

Answer 6

astral, kinetochore and interpolar

Question 7

Dyenin

Answer 7

minus end directed, organises Mts at various locations, link + end of astral Mts to actin cytoskeleton

Question 8

Kinesin 4 and 10

Answer 8

“chromokinesins”

+ end directed, attach chromosome arm and push away from pole

Question 9

Kinesin 14

Answer 9

minus end directed

single motor domain cross link interpolate Mts and pull them together

Question 10

kinesin 5

Answer 10

2 motor domains, interact with the plus ends of antiparallel MT in spindle mid zone

move towards the plus ends, slide Mts past each other -towards poles, pushing the poles apart

Question 11

in a xenopous egg what regulates the catastrophe rate and the Mt length

Answer 11

a single catastrophe factor and MAP

Question 12

3 forces that move the chromosome along the spindle

Answer 12

• kinetochore + associated chromosome pulled towards the pole - doesn’t require ATP, energy comes from GTP
• microtubule flux - Mts move so do the poles, then they dismantle from the - end
• polar ejection force - kinesin 4 and 10 (+ended) align bioriental sister chromatids at metaphase plate

Question 13

cytokinesis

Answer 13

• cytoplasmic bundle of stress fibres
• assembly of contractile ring - nucleated by forming proteins - parallel arrays
• actin and myosin contracting the ring

Question 14

Rho - contractile ring

Answer 14

RhoA - formin - actin filament - assembly ring

Question 15

what role do Mts have in cytokinesis

Answer 15

they control the position of the division plane

Question 16

where are Mts nucleated from

Answer 16

the Y TURC complex

Question 17

Ndc80

Answer 17

helps to attach chromosomes to MTs

Question 18

cofilin

Answer 18

actin growing from the leading edge, coffin disassembles the F actin from behind recycling it

twists the actin branches - break them into fragments

Question 19

recent research dhows that

Answer 19

coffin can also be found at the leading edge

Question 20

Mts dont form

Answer 20

branches

Question 21

Mts in intracellular trafficinf

Answer 21

are used as long tracks which vesicles are transported on using kinesis and dyeing motors

Question 22

actin mediated intracellular trafficing

Answer 22

short distance