α-Keratin has all of the following characteristics EXCEPT:
a. primary component in hair, claws, fingernails, and horns of animals.
b. consists of four helical strands arranged as twisted pairs of two-stranded coiled coils.
c. has associated hydrophobic strips on the two coiled coils.
d. principal constituent of connective tissues in animals.
e. has covalent disulfide bonds to stabilize the structure.