Describe the helical and coiled-coil structures of either collagen or α-keratin. What type of covalent bond holds the coiled-coils in staggered arrangements to form larger fibrous structures of this protein?

Collagen is an extracellular matrix protein and one of the most abundant protein in the body. Its triple-helical structure is a result of the 3 coiled chains. Each chain mainly comprises of Glycine, Proline and Hydroxyproline. The Glycine hydrogen bonds with residues of the adjacent chain while the proline and hydroxyproline C-N bonds provide stability in the structure.