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Protein Structure Levels
- 1. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Introduction to protein structure Bilal El Houdaigui National School of Applied Science of Tangier bilal.elhoudaigui@gmail.com September 22, 2016
- 2. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Outline 1 Introduction Importance of protein structure Some definitions 2 Primary structure Definition Characteristics 3 Secondary structure Characteristics & Types Alpha Helix Beta sheet 4 Tertiary structure Characteristics Interactions 5 Quaternary structure Characteristics 6 Recap 7 Conclusion
- 3. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Importance of protein structure Proteins are the building blocks of all cells. In the world of proteins: Structure ≡ Function! DNA encodes life..Yes! But proteins carry out life processes, replication, reproduction, defense etc!
- 4. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Protein Protein Proteins are large macromolecules, consisting of one or more long chains of amino acid residues. Figure 1: A representation of the 3D structure of the protein myoglobin
- 5. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Amino Acide Structure (1/2) Definition Amino acids are biologically important organic compounds containing amine (-NH2) and carboxylic acid (-COOH) functional groups, usually along with a side-chain (R group) specific to each amino acid. The key elements of an amino acid are : Carbon Hydrogen Oxygen Nitrogen Figure 2: The structure of an amino acid
- 6. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Amino Acide Structure (2/2) Figure 3: Twenty different types of side chains (20 amino acids)
- 7. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Peptide Peptide Peptides are biologically occurring short chains of amino acid linked by peptide bonds. Figure 4: Tetrapeptide structural formulae Polypeptide is a long, continuous, and unbranched peptide chain.
- 8. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Peptide bond Peptide bond A peptide bond is a covalent chemical bond linking two consecutive amino acid along a peptide or protein chain. Figure 5: Peptid formation
- 9. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Covalent bond Covalent bond A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. Figure 6: Covalent bond - hydrogen
- 10. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Primary structure : Definition Definition The primary structure of a protein refers to the linear sequence of amino acids in the polypeptide chain. The primary structure is held together by covalent bonds such as peptide bonds. Figure 7: Primary protein structure (a)
- 11. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Primary structure : Characteristics Characteristics Unique sequence of amino acid. Sequence determined by DNA. Amino acids are covalently linked by peptide bonds. By convention, the structure of a protein starts from the amino-terminal (N) end and ends in the carboxyl-terminal (C) end. Figure 8: Primary protein structure (b)
- 12. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Secondary structure : Characteristics & Types Characteristics Results from hydrogen bonds at regular intervals along the polypeptide backbone. Not found in all proteins. Two major Types of secondary structure: 1 α-helix. 2 β sheet.
- 13. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Secondary structure : Alpha Helix Characteristics of the alpha-Helix structure: Spiral structure. Tightly packed, coiled polypeptide backbone core. Side chain extend outwards. Stabilized by H bonding b/w carbonyl oxygen and amide hydrogen. The helix has 3.6 residues per turn. Figure 9: Alpha Helix
- 14. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Secondary structure : Beta sheet Characteristics of the beta sheet structure: Each β strand is fully extended. Stabilized by H bonding b/w carbonyl oxygen and amide hydrogen the of adjacent chains. Types of the beta sheet: Parallel β sheet. Antiparallel β sheet. Figure 10: Beta sheet
- 15. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Tertiary structure : Characteristics Characteristics Tertiary structure is the three dimensional conformation of a polypeptide. The common features of protein tertiary structure reveal much about the biological functions of the proteins and their evolutionary origins. The function of a protein depends on its tertiary structure. If this is disrupted, it loses its activity. Figure 11: Tertiary structure
- 16. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Tertiary structure : Interactions Interactions between: R groups and R groups. R groups and backbone. Types of interaction: Hydrogen bonds Ionic bonds. Hydrophobic interactions (Often in interior of protein) Covalent bonds (Disulfide bridge: formed between the sulfhydryl groups (SH) of cysteine amino acids). Figure 12: interactions in tertiary structure
- 17. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Quaternary structure : Characteristics Characteristics Aggregation of two or more polypeptide subunits. Not found in all proteins. Hemoglobin (Example): Hemoglobin is a protein that exist in the red blood cells. It carries oxygen from the respiratory organs to the rest of the body. Figure 13: Structure of human hemoglobin
- 18. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Recap https://www.youtube.com/watch?v=qBRFIMcxZNM
- 19. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Conclusion Proteins are extraordinarily complex molecules. Of all the molecules encountered in living organisms, proteins have the most diverse functions. So a basic understanding of the structure of proteins is necessary to comprehend its role in organisms. Further researches will provide more insight into the structure of several other proteins in the coming year.
- 20. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion The End
- 21. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Annex
- 22. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion Disulfide bond Definition A disulfide bond, also called an S-S bond, or disulfide bridge, is a covalent bond derived from two thiol groups. In biochemistry, the terminology R-S-S-R connectivity is commonly used to describe the overall linkages. Figure 14: Formal depiction of disulfide bond formation as an oxidation
- 23. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion What Is the Difference Between a Peptide and a Protein? Peptide VS Protein The basic distinguishing factors are size and structure. Peptides are smaller than proteins. Traditionally, peptides are defined as molecules that consist of between 2 and 50 amino acids, whereas proteins are made up of 50 or more amino acids. In addition, peptides tend to be less well defined in structure than proteins, which can adopt complex conformations known as secondary, tertiary, and quaternary structures. Figure 15: Protein, Peptide and Amino Acid
- 24. Structure of proteins Introduction Why ? Some definitions Primary structure Definition Characteristics Secondary structure Characteristics & Types Alpha Helix Beta sheet Tertiary structure Characteristics Interactions Quaternary structure Characteristics Recap Conclusion References https://en.wikipedia.org/wiki/Protein https://en.wikipedia.org/wiki/Peptide_bond https://en.wikipedia.org/wiki/Covalent_bond https://en.wikipedia.org/wiki/Amino_acid http://www.personal.psu.edu/staff/m/b/mbt102/ bisci4online/chemistry/chemistry8.htm https://en.wikipedia.org/wiki/Hemoglobin https://www.youtube.com/watch?v=qBRFIMcxZNM https://en.wikibooks.org/wiki/Structural_ Biochemistry/Chemical_Bonding/_Disulfide_bonds https://www.britannica.com/story/ what-is-the-difference-between-a-peptide-and -a-protein