Question

You are examining two cytoskeletal filaments that you have never previously observed. You have been able to purify them and have named them Dipper and Mabel. You want to see if these new cytoskeletal elements (which you are certain are NOT actin, microtubules or intermediate filaments) behave similarly to actin or microtubules.

A)You start to examine the cytoskeletal filament Dipper which has a rounded end and a sharp end. You are growing your novel Dipper filament at low, intermediate and high concentrations of monomer and are observing how it is growing. You discover that at low concentrations of Dipper monomer the​ filament starts to disassociate from the rounded end​, that at intermediate concentrations the ​filament neither loses subunits, nor gains subunits​ and at high concentrations of Dipper monomer the ​filament grows from the sharp end​. ​Compare and contrast how this filament behaves compared to actin at low/medium/high monomer concentration.

B) Upon examining Mabel filament more closely you find that it forms curly strands that grow from both ends and occasionally will suddenly shrink​. When you sever Mabel to make two smaller Mabel filaments you find that ​both strands rapidly fall apart from the site of cleavage​. C​ ompare the normal growth/shrinkage of these filaments and shrinkage upon severing with how microtubules behave during normal growth and upon severing

Answer 1

ans. a) actin filament is one of the most abundant and conserved protein in eukaryotic cell. it conain G-actin which globular protein and is monomer of actin filament while f-actin which is fibrous and polymer of actin.

actin polymerizes in three phases i.e. nucleation phase, elongation phase ans steady-state phase. in nucleaton phase, monomers added and forms polymer at slow rate, in elongation phase monomera added at very fast speed and durin steady phase number of monomer added and release are same i.e. added from one side and release from another side. actin bhaviour at low/mdium and high monomer concentration is different from dipper polymerization while the structure is also diffrent.

b) microtubules fall apart because a layer of non-hydrolyzed, relatively stable GTP-tubulin remain at the end. if the protective cap is lost it begins to splay and tera out from the polymer which makes it shrink. as mabel grow from bpth the sides microtubules also grow form both the sides.