Question

1. What is the advantage of constructing cytoskeletal filaments from multiple protofilaments? What is the difference between the + and – ends of a cytoskeletal filament? How might you account for this difference? Why don’t intermediate filaments have + and – ends?

Answer 1

Cytoskeletal filaments have strength combined with adaptability. In order to achieve this only multiple protofilaments are involved in constructing cytoskeletal filaments.

Cytoskeletal filaments have positive and negative ends. "Having positive and negative ends" is important to regulate at opposite ends of the filament. Addition of new monomers is faster at the positive than the negative end. Typically, the positive end is directed towards the membrane.

Intermediate filaments are assembled from antiparallel tetramers. So, both ends of intermediate filaments are equivalent.