Collagen vs Keratin
(Similarities and Differences between Collagen and Keratin)
Collagen and Keratin are the main structural proteins. They are two main families of fibrous proteins and are abundantly present in the extracellular matrix and various connective tissues in animals.
Collagen: A linear structural fibrous protein abundantly found in the connective tissue and extracellular space of the cells. They are also found in tendons, ligaments, cornea, cartilage, bone, blood vessels, intervertebral discs and the dentine in teeth.
Keratin: A structural protein abundantly present in epithelial cells. They protect the epithelial cells from damage or stress. Keratin is also present in appendages such as feathers, hairs and nail, horn, claws and hooves of animals. Keratin is the structural material that makes the human skin.
The present post discusses the similarities and Differences between Collagen and Keratin with a Comparison Table.
Similarities between Collagen and Keratin
Ø Both collagen and keratin are structural proteins.
Ø Both are linear and fibrous proteins.
Ø Both are very insoluble in water and organic solvents.
Ø Both are with high tensile strength.
Ø Both are with complex triple helical structures.
Ø Both are present in the extracellular matrix of cells (proportion varies).
Difference between Collagen and Keratin
Sl. No. Collagen Keratin
1 Collagen is abundantly found in the ECM and in connective tissues. Keratin is mainly seen in the epithelial cells and in appendages such as feathers, hairs and nail, horn, claws and hooves.
2 Collagen is rich in an unusual amino acid hydroxyproline. Also abundant in glycine, Proline and Alanine. Keratin is rich in hydrophobic amino acids such as Phenylalanine, Isoleucine, Valine, Methionine and Alanine.
3 The polypeptide chains in the collagen are left-handed. The polypeptide chains in keratin are right-handed.
4 Three helical strands wrap together into a repeatedly superhelical structure called tropocollagen. Three helical strands wrap together in a super-helical structure called protofibril.
5 The superhelical twisting in tropocollagen is right-handed. The superhelical twisting in protofibril is left-handed.
6 Lysinonorleucine, an unusual amino acid residue formed the covalent link between Lysine residues in the polypeptide chain contribute the cross-links between the chains. Disulphide bonds that occur between the polypeptide chains within the triple helical structure contribute the cross-links.
7 In human 28 different types of collagen are described, among these Type I, II, III, IV, V, XI are common. Type I is most abundant (90% of collagen). In human, two types of keratins are described, Type I and Type II
8 Collagen is not involved in the cortification process. Production of Keratin is involved in the cortification of epithelial cells.
9 Very few non-fibrillar collagens present in the collagen-family All are fibrillar proteins in the Keratin-family
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