is a-keratin before it coils with another polypeptide, makes chains, and build intermediate fillaments a fully functioal protein?
I mean, is the single monomer of a-keratin a protein or it has to become a dimer to become a protein?
What we call as protein is the final quaternary structure. Whether it is translated from a single gene or from multiple genes (as in haemoglobin), always the structure with all bonds and interactions taken into account. Similarly here the alpha- Keratin forms Disulfide bonds to form a functional protein.