Final answer:
The two main characteristic structures of collagen include the triple helix formation for strength and elasticity, and a unique amino acid sequence (-Gly-X-Y) that contributes to its stability. Glycine is critical in this structure as it is found every third position, facilitating the tight packing of the triple helix.
Step-by-step explanation:
Characteristics Structures of Collagen
One of the main characteristic structures of collagen is the triple helix. This secondary structure gives collagen its characteristic strength and elasticity, which is essential for its role in connective tissues such as tendons, cartilage, blood vessels, skin, and bones. Collagen is a fibrous protein and is the most abundant protein in vertebrates.
The second characteristic is its unique amino acid composition, with a repeating sequence of -Gly-X-Y, where 'X' is often proline and 'Y' is often hydroxyproline or hydroxylysine. This composition allows tight packing of the three chains in the triple helix and contributes to the overall stability and strength of the collagen fibrils. Hydroxyproline and hydroxylysine are important for the stabilization of the triple helix and are created via posttranslational modification.
Glycine, being the smallest amino acid, plays a critical role in the compact structure of the triple helix because it is found in every third position of the polypeptide chain. Proline and hydroxyproline confer rigidity, which is a key aspect of the structural role of collagen in the connective tissues.