Hierarchial Structure of Collagen

Hierarchial Structure of Collagen,
Disorders, Uses, Micro fibrils , Fibrils

1. HIERARCHIAL STRUCTURE OF COLLAGEN Presented By : Prashant Waiba A-22 Bishwas Dotel B-17 1

2. Collagen Overview 2 Collagen : Most abundant protein found in the human body. About 1/3 rd of the total proteins. Location : abundantly in tendon, cartilage, bone and skin Functions : Cell migration Cell adhesion Tissue repair collagen fiber in ECM

3. 3 Structure of Collagen Secondary Structure > Brought about by intrachain H-bonds > HydroxyPro and HydroxyLys - participate in the intrachain H-bonds which stabilizes the entire molecule. >Three residues per turn Primary Structure > Peptide chain (made up of amino acids) > ( Gly -X - Y)n > Gly - every 3rd residue (to ensure tight packing due to its small R group) > 1000 + residues

4. 4 Structure of Collagen Tertiary Structure > Interchain H-bonds > Hydrophobic interaction > Disulfide bonds > Triple helix Quaternary structure > Cross linking between tropocollagen units > Schiff base and aldol residues further increases the cross linking ( covalentbonds ).

5. Molecular Collagen 5 The Basic Structural Unit of Collagen Is Triple Helix of 3 polypeptide chains. Polypeptide chains Glysine ( Gly )-X-Y repeating triplet of amino acid residues (from Beck, 1998)

6. Polypeptide Chains Terminals (ends) of the triple-helix are different C- telopeptides N- telopeptides The terminals of collagen are non-helical. Play important roles in microfibril and fibril formation 6 (from Kadler , 1996)

7. Triple-helix conformation Gly must occupy every third residue Side chain is a hydrogen atom only Small enough to fit inside the helix Gly aligned with X residue of one chain and Y residue of third chain Staggered arrangement in helix by one residue Mutation that causes replacement of Gly leads to defective molecules and disease Osteogenesis Imperfecta 7 Polypeptide Chains: Three chains of triple helix

8. Typically X-position occupied by Proline (Pro) Y-position occupied by Hydroxyproline ( Hyp ) Function Pro and Hyp : triple-helix stability Other Intermolecular binding Binding to extracellular matrix molecules 8 Polypeptide Chains: Collagen molecule

9. 9 TRIPLE HELIX Amino Acid residues in collagen. Gly , Pro and Hydroxyproline residues present in a collagen molecule Geometry Right-handed coil 300 nm length 2.8 A° helix radius 1.5 nm molecular diameter

10. TRIPLE HELIX Structural unit of collagen is a tropocollagen , a supercoil made up of 3 helices, with a molecular mass of ~285 kdal . The collagen triple helix is stabilized by an interchain hydrogen bonding network involving the hydroxyl group of hydroxyproline , the glycine carbonyl group, and water molecules . 10 Fig: Hydrogen Bonds in collagen atom

11. 1 H-bond per triplet. The presence of hydroxyproline in the Y position is also thought to contribute to the stability of the helical form. C- telopeptides & N- telopeptides of each chain are aligned Winding C  N The proper folding of each of these chains requires a glycine residue to be present in every third position in the polypeptide chain . 1000 amino acid residues. The helix contains 3 amino acids per turn, with a pitch of 0.94 nm. 11 TRIPLE HELIX

12. Types of Collagen More than 20 types Type determined by polypeptide sequence Properties vary by type Fibril forming Types I, III, V, XI Most common collagen: Type I, contains two chains called α 1 and α 2 Type II, collagen contains three α 1 chains 12

13. 13 Types of Collagen

14. Collagen: Used For? F or many things inside our bodies; from giving us strength to making us seem youthful . For mainly in and around the bones as it gives tendons greater strength , and preventing rips in tendons. For strengthening bones, which when old age is reached there is a lack of collagen, making bones brittle . On skin, for holding the skin together. People also believe that collagen gives mammals the shinier skin and without wrinkles, high amount of collagen would lead to young and softer skin. ( unfortunately amount of collagen reduces, in ageing). 14

15. 15 FORMATION OF COLLAGEN

16. FORMATION OF COLLAGEN 16 SEQUENCE OF EVENTS A. Sequence of intracellular collagen biosynthesis: Assembly pro- alfa chains (directed by specific mRNAs) Proline hydroxylation Hydroxylysine glycosylation Disulphide bond formation/incorporation of C Terminal Propeptides secretion

17. 17 FORMATION OF COLLAGEN B. Sequence of extracellular collagen biosynthesis Amino terminal extension cleavage Carboxyl terminal extension cleavage Microfibril formation Lysine hydrolxylysine terminal NH2 oxidation ( Cu-containing lysyl oxidase) Fibril formation Reducible crosslink formation Maturation of cross-links. Growth and reorganization of fibers

18. Molecules to Microfibrils 18

19. Microfibrils Microfibril is building block of fibrils 5 collagen molecules in 1 microfibril Entropy driven self-assembly process Smallest unit that contains 1 D repeat D = 67 nm 19 (from Kadler, 1995)

20. Molecules broken down into 5 segments 4 segments of length D (segments 1-4) 1 segment of length 0.46D (segment 5) Segments 1 & 5 contain the telopeptides Intermolecular cross-links Provide structural integrity & strength 20 Microfibrils (from Piez , 1984)

21. Cross-links Segment 1 cross-links with segment 5 between adjacent molecules Aldehyde cross-link Between lysine and allysine in the telopeptides 21 Microfibrils (from Orgel, 2001)

22. Microfibrils to Fibrils 22

23. Microfibrils to Fibrils Alignment of microfibrils Longitudinal C-terminal aligns with the N-terminal Never N-N alignment C-C fusion possible  polarity transition region N-terminal always oriented towards the growing tip of the fibril Lateral Cross-linking between microfibrils Alignment of the C-terminal to the shaft of neighboring molecule Branched network  stability Diameter growth in increments of ~8 nm 23

24. 24 Microfibrils to Fibrils (from Prockop , 1998) (from Orgel , 2002)

25. 25 Fibrils (from Hulmes , 2002)

26. 26 Fibrils Geometry Left-handed coil Length and diameter varies 30 – 500 nm diameter Dependent on tissue, age, genetics Microfibrils aligned at 17° from fibril axis

27. Collagen Disorders Ehlers- Danlos syndrome (collagen I and V ) Stretchy skin Alport syndrome (collagen IV ) Dentinogenesis Imperfecta Opalescent and cracked teeth Subtypes of osteogenesis imperfecta (collagen I) Known as Brittle Bone Syndrome. 27 Fig: Ehlers- Danlos Syndrome Fig: Dentinogenesis Imperfecta

28. Conclusion At the end we can conclude; Collagen is the most abundant human protean Triple helical structure consisting of repeating sequence of ( Gly -X - Y)n Basic foundation of vital largest organ ; skin COMMON TYPES Type I: bone , tendon, fibrocartilage, dermis, cornea Type II: nucleus pulposus , hyaline cartilage Type III: intestinal and uterine wall Type IV: endothelial , epithelial membranes Type V*: cornea , placenta, bone, heart valve 28

29. References 29 "Biomaterials-lecture7-new.ppt"- Er . Neela Prajapati http :// kentsimmons.uwinnipeg.ca/cm1504 Ratner Buddy D., Et .al Biomaterial Science:An Introduction to Materials in Medicine . http://chemistry.about.com/od/polymers/a/Collagen.htm http:// www.sciencedirect.com/science/article/pii/S0065323305700097 http://www.mdpi.com/

30. THANK YOU !! 30

31. ANY QUERIES ? 31