MAPs and ABPs Flashcards
Stathmin
MAP - inhibited during mitosis by phosphorylation
- normally binds to tubuulin and inhibits MT polymerisation
- increases likelihood of catastrophe
phosphorylation of stathmin
inhibits interaction with tubular - so tubular can polymerise to form Mts
how many molecules of tubular does stathmin bind
2 heterodimers
stathmin over expression in cancer cells
cancer cells frequently over express stathmin - inc. rate of MT turnover - contribute to change in cell shop and associated with malignant transformation
which protein is though to phosphorylate stathmin in the cell cycle
cdc2
3 types of Mts in a cell undergoing mitosis
astral, kinetochore and interpolar
Dyenin
minus end directed, organises Mts at various locations, link + end of astral Mts to actin cytoskeleton
Kinesin 4 and 10
“chromokinesins”
+ end directed, attach chromosome arm and push away from pole
Kinesin 14
minus end directed
single motor domain cross link interpolate Mts and pull them together
kinesin 5
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
in a xenopous egg what regulates the catastrophe rate and the Mt length
a single catastrophe factor and MAP
3 forces that move the chromosome along the spindle
- 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
cytokinesis
- cytoplasmic bundle of stress fibres
- assembly of contractile ring - nucleated by forming proteins - parallel arrays
- actin and myosin contracting the ring
Rho - contractile ring
RhoA - formin - actin filament - assembly ring
what role do Mts have in cytokinesis
they control the position of the division plane
where are Mts nucleated from
the Y TURC complex
Ndc80
helps to attach chromosomes to MTs
cofilin
actin growing from the leading edge, coffin disassembles the F actin from behind recycling it
twists the actin branches - break them into fragments
recent research dhows that
coffin can also be found at the leading edge
Mts dont form
branches
Mts in intracellular trafficinf
are used as long tracks which vesicles are transported on using kinesis and dyeing motors
actin mediated intracellular trafficing
short distance
