Lecture 2: Cytoskeletal Networks Flashcards
different types of polar cytoskeleton organization
microtubules
actin
intermediate filaments
microtubules
can transport vesicles and proteins to different ends of the cell
actin
important for defining cell shape and behaviour
intermediate filaments
contribute to cell polarity
what is the structure of microtubules
they are long, hollow tubes
These tubes are made from individual subunits of b-GTP and a-GTP which attach to form a protafilaments and 13 protofilaments will form a hollow tube
The tube will have polarity as the B end is the plus end and a-side is minus
if you have GTP at the end of your microtubule, would you expect to have more or less growth? Why
we would expect to see more growth because GTP-bound tubulin heterodimers encourage growth of the microtubules
dynamic instability
The filament will undergo rapid extension if GTP hydrolysis is slower than the addition of an-tubular dimer
This growth will form a GTP-cap
Shrinking happens when GTP hydrolysis is faster than the addition of T-form heterodimers
During this process,the GTP-Cap is lost and now instead of T-form, you have D-form heterodimer which will fall off due to weaker bondswhen the GTP gets hydrolyzed to GDP, this decreases binding affinity causing the tubulin to break off and disassemble
y-tubulin
helps to nucleate microtubules by interacting with the alpha tubulin at the minus end and stabilizing it and preventing depolymerization at the minus end
where is y tubulin located in animal cells?
it is located on the sphere of the microtubule on pericentriole
where is y tubulin located in plant cells?
they situated on other microtubules
how can vesicles be transported along microtubules?
microtubules often have kinesins (toward positive end) or dyneins (toward minus end) that walk along the microtubules and can attach to vesicles or organelles walking it to its destination
example of animal using microtubules
talapia fish use microtubules to change colours, dark pigmentation in fish occur when the microtubules walk and disperse the pigmentation along the cell where as light coloured fish have their pigment concentrated into one area
describe actin treadmilling
you can have addition of actin monomers on both sides of the filament, where T form (atp bund) is being added to plus end and slow addition to the minus end however you have much more D form (ADP bound) to the minus end causing depolymerization
what is used to help nucleate actin filaments
ARP2/3 complex
ARP 2/3 complex
these complexes are actin related proteins that help nucleate the minus end of actin filaments and protects it from depolymerization
