The intermediate filament network is a dynamic network that forms in many cell types. Intermediate filaments are composed of a large number of diverse subunit that can form either homo-oligomers or hetero-oligomers. Their assembly mechanism involves the initial parallel dimerization of two intermediate filament subunits. This dimeric unit then associates in an anti-parallel manner to form a tetramer, which is the basic building block of intermediate filament assembly.
Keratins are major components of skin epithelial cells. Multiple disorders have been associated with mutations in keratins. Because epithelial cells usually serve as a protective barrier for the skin, defects in the keratins usually lead to blistering of the skin.
Questions:
1. Based on the structure of individual keratin subunits, why would a single point mutation in the alpha-helical region of the monomer result in a defect in the polymer? ( 0.5 pts)
2. An alternative model is that the mutations cause defect intermediate filaments with defective structure that causes problems in the ability of motor proteins to transport material on these filaments. Is this a plausible model? Why or why not? ( 0.5 pts)