MICROTUBULE STRUCURE AND FUNCTION Flashcards
Which pair is most similar between microfilaments, microtubules and intermediate filaments
Microfilaments/tubules are most similar, both are highly dynamic and polarised. Both have a motor like function
Intermediate filaments are less dynamic unpolarised and have no motors.
How do microtubules grow?
Motor proteins recognise ends and usually grow at the positive end via fast polymerisation , causing a treadmilling effect when rate of polymerisation is equal to depolarisation.
What are microtubules made of?
a and B tubulin dimer
GTP’s role?
GTP bound b-tubulin (T form) undergoes slow hydrolysis to GDP so that GDP bound b-tubulin (D form) is the predominant.
How is capping involved in treadmilling?
In many cases the minus end of microtubules is capped so that growth and shrinkage of microtubules occurs only at the plus end. However in some circumstances (such as in mitosis) the minus end is free to undergo disassembly while the plus end is polymerising giving rise to the phenomenon known as treadmilling.
Which region or MT is less stable?
GTP cap is stable
Less stable region contains GDP tubulin dimers
Why are elongating filaments straight while shrinking filaments have flayed ends.
Microtubule assembly is favoured when microtubule is straight. Hydrolysis of b-tubulin bound GTP to GDP causes a conformational change in the a,b tubulin dimer which tenses the MT lattice. The protofilaments splay outwards when depolymerising but are prevented from doing so when the microtubule is polymerising by the presence of the GFP-tubulin cap.
How do microtubules grow during mitosis?
During mitosis spindle microtubules in animal cells undergo microtubule flux because the minus end of microtubules can now undergo depolymerisation at the spindle poles. This aids the establishment of chromosome orientation.
anaphase.
