Collagen Structure & Function

IntroductionIntroduction

Collagen is a member of a naturally occurring protein family. It is one of the most plentiful proteins present in mammals and is responsible for performing a variety of biological functions. It is present in large quantities in connective tissue and provides tendons and ligaments with tensile strength and skin with elasticity.It often works in conjuction with other important proteins such as keratin and elastin.

Molecular StructureMolecular Structure

The shape and structural properties of a native collagen molecule are established by its triple-helical domain(s). In classical collagen molecules a single triple-helical domain is observed to compose close to 95% of the molecule. However there are also other types of collagens that have been shown to comprise of multiple triple-helical domains which only account for a fraction of the molecules mass.

The triple-helical domain of collagens consist of three distinct α-chains. Each of these chains contain a characteristic L-handed amino acid sequence of polyproline, often termed as polyproline type II helix. The proper folding of each of these chains requires a glycine residue to be present in every third position of the polypeptide chain. For example, each α-chain is composed of multiple triplet sequences of of Gly-Y-Z in which Y and Z can be any amino acid. Y is commonly found as proline and Z as hydroxyproline. The presence of hydroxyproline in the Y position contributes to the stability of the helical form.

These three chains are then twisted around one another in a rope-like manner to produce the overall tightly packed triple-helical form of the molecule. The interaction of α-chains is stabilized via interchain hydrogen bonding making the molcule fairly resistant to attack by other molcules. This hydrogen bonding occurs when the NH of a glycine residue forms a peptide bond with the C=0 of an adjacent residue. The overall molecule is approxiametly 300nm long and 1.5-2nm in diameter.

FunctionFunction

There are currently close to 30 different types of collagen that have been identified . The most abundant type of collagen present in the human body is that of Type I with significant amounts of Type II,III and IV also accounted for.

• Collagen I- found in bones,tendons,organs
• Collagen II-found mainly in cartilage
• Collagen III-found mainly in reticular fibres
• Collagen IV-found in the basement membrane of cell membranes
• Collagen V-found in hair

Collagen-Related DisordersCollagen-Related Disorders

There are many types of disorders associated with collagen. These include:

• Elhers-Danlos Syndrome
• Alport Syndrome
• Osteogenesis imperfecta
• Chondrodysplasias
• Atopic Dermatitis

ReferencesReferences

Bella J, Eaton M, Brodsky B, Berman HM Crystal and molecular structure of a collagen-like peptide at 1.9A resolution Science v266, p.75-81

spinqualitylabelsall models PDB ID 1cag Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image
1cag, resolution 1.85Å ()
Ligands:
Non-Standard Residues:
Resources:	FirstGlance, OCA, PDBsum, RCSB
Coordinates:	save as pdb, mmCIF, xml