Which of the following intermediates of intermediate filamen

Which of the following intermediates of intermediate filament assembly is polar?

Dimer

Tetramer

Octamer

Intermediate filament bundle

None, intermediate filaments are always apolar

Solution

Intermediate filaments are structural proteins that provide mechanical strength to cells and tissues. Unlike actin or microtubules which are polymers of a single protein, intermediate filaments are made of different proteins. Till date, more than 50 different sub types of intermediate filaments have been discovered.

During filament assembly, two polypeptide chains wind around each other forming a coiled dimer. Dimers then associate in a staggered anti-parallel position to form tetramers, which then assemble end-to-end forming proto-filaments. Eight protofilaments wind around each other to form an Intermediate filament.

Since the filaments are assembled from anti-parallel tetramers, they lack distinct minus and plus ends, making them apolar.

Therefore, the correct option is Option 5: None, Intermediate Filaments are always apolar.