Structure of Collagen (PDB entry 4clg or 1cag) . It consists of a triple helix made of the repetitious amino acid sequence glycine-X-Y, where X and Y are frequently proline or hydroxyproline. 1. This structure is called collagen helix. Collagen folded into a triple helix is known as tropocollagen. PDB ID 1cag . Primary, secondary and tertiary structures are descriptions of a single polypeptide.  This contact is impossible even when a slightly bigger amino acid residue is present other than glycine. 5, 2008, pp. It can also be elastic, as in skin, and flexible, as in a … Glycine, proline, and hydroxyproline must be in their designated positions with the correct configuration. The pyrrolidine rings keep out of each other's way when the polypeptide chain assumes this extended helical form, which is much more open than the tightly coiled form of the alpha helix. The molecular structure of collagen mainly depends on the secondary structure of the polypeptide chain .Pyrrolidine rings of proline and hydroxyproline are mainly responsible for the unique structure of collagen and the helical stability is directly proportional to the amino acid content . Caused by a mutation in one or the other of the two genes whose products are used to make Type I collagen.  The thermal stabilization is also hindered when the hydroxyl group has the wrong configuration. The basal lamina of the lung epithelia and the glomeruli of the kidney are especially likely to be affected. The OH group of hydroxyproline does not participate in hydrogen bonding but stabilises the trans isomer of proline by stereoelectronic effects, therefore stabilizing the entire triple helix. The structures of keratin illustrate the importance of secondary structure in giving proteins their overall properties… Most cases involve mutations in the gene on the X chromosome for one of the chains of Type IV collagen. "Crystal structure of the collagen triple helix model [(Pro-Pro-Gly)(10)](3)". Collagen has a quaternary structure since it is made up of 3 polypeptides (3 alpha helicies)... (Each polypeptide of collagen has secondary structure) Primary Structure of Collagens The basic unit of collagens is a polypeptide consisting of the repeating sequence (glycine (Gly) - X - Y) n. where X is often proline (Pro) and Y is often hydroxyproline (proline to which an -OH group is added after synthesis of the polypeptide). Each of the three chains is stabilized by the steric repulsion due to the pyrrolidine rings of proline and hydroxyproline residues. Harpers Illustrated Biochemistry, 30th edition. 1001–1025. Berisio R, Vitagliano L, Mazzarella L, Zagari A (February 2002).  Due to the very tiny and tight space at the center, only the small hydrogen of the glycine side chain is capable of interacting with the center. Collagen is a fibrous protein, the major component of the connective tissue, skin, tendons, cartilage and bones. In collagen we can find a singular secondary structure, helicoidal but more stretched or elongated than alpha helix and turning left instead of right-handed. Collagen helix. “Collagen Structure: New Tricks from a Very Old Dog.” The Biochemical Journal, vol. The rise of the collagen helix (superhelix) is 2.9 Å (0.29 nm) per residue. "Crystal structure of the collagen triple helix model [(Pro-Pro-Gly)(10)](3)", https://en.wikipedia.org/w/index.php?title=Collagen_helix&oldid=981390183, Creative Commons Attribution-ShareAlike License, This page was last edited on 2 October 2020, at 01:08. Once you have 2 or more polypeptides interacting with each other (e.g., Hemoglobin molecule) you have quaternary structure. It is found in particularly high amounts in tissues that need to be strong, flexible or both, including cartilage, bones and tendons. 2. Collagen provides structure to our bodies, protecting and supporting the softer tissues and connecting them with the skeleton. Collagen is a major structural protein, forming molecular cables that strengthen the tendons and resilient sheets that support the skin and internal organs. The hydrogen bond donors are the peptide NH groups of glycine residues. These are called phi and psi. As they pass through the endoplasmic reticulum (ER) and Golgi apparatus. Brodsky, Barbara, et al.  A collagen triple helix has 3.3 residues per turn.. , , , --((( PDB ID 4clg . In collagen we can find a singular secondary structure, helicoidal but more stretched or elongated than alpha helix and turning left instead of right-handed. Bella, Jordi. Other cases are caused by two mutant autosomal genes for another of the Type IV collagen chains. For example, collagen forms part of the matrix upon which cells are arranged in animal tissues. But, in spite of its critical function in the body, collagen is a … Gly Packing in 4clg Ala Packing in 1cag (Mutated Collagen) In order to convince yourself that there is a difference in the interchain distances in the area of the Ala, between Gly (Ala) and Pro which form intratropocollagen hydrogen bonds. The reason: even though one collagen allele is normal, the assembly of the normal gene product with the mutant product produces defective collagen fibers. For example, hydroxyproline in the Y position increases the thermal stability of the triple helix, but not when it is located in the X position. So Goodpasture's syndrome is an example of an autoimmune disorder. Like all the inherited collagen diseases, this one is inherited as a dominant trait. When synthesized, the N- terminal and C- terminal of the polypeptide have globular domains, which keep the molecule soluble. It consists of a triple helix made of the repetitious amino acid sequence glycine-X-Y, where X and Y are frequently proline or hydroxyproline. Brittle-bone disease ("osteogenesis imperfecta"), the most abundant proteins in the human body. It is the principal structural element of the human body and makes up 25% o 33% of all the body protein. Due to the high abundance of glycine and proline contents, collagen fails to form a regular α-helix and β-sheet structure. The collagen triple helix or type-2 helix is the primary secondary structure of various types of fibrous collagen, including type I collagen. The major ones are: The other 25 types are probably equally important but they are much less abundant. So this disease now seems to be a promising candidate for gene therapy. A perfect helix structure (covered later) needs both phi (Φ) and psi (Ψ) to be at an angle of about -60 de… In other collagens (e.g., Type I), two polypeptides of one kind (gene product) assemble with a second, quite similar, polypeptide, that is the product of a second gene. The length of the peptide bond is between these, at 1.28Å.