types of secondary structure and super secondary structure of protein

this slides will explain about alpha helix and beta pleated sheets, and types of super secondary structures

1. TYPES OF SECONDARY STRUCTURE & SUPER SECONDARY STRUCTURE OF PROTEIN Presented by: LEO PRABHA. A 1 st year MSc Biotechnology Dayananda Sagar University Guided by: Dr. ROSHAN SIR Assistant professor Dayananda Sagar University MSc. Biotechnology 1 st semester/ seminar session 2021

2. CONTENT MSc. Biotechnology 1 st semester/ seminar session 2021 Introduction Alpha helix Alpha keratin Beta sheets Super secondary structure Domains Conclusion Reference

3. INTRODUCTION Proteins – biological macromolecules It consists - Primary structure - secondary structure - tertiary structure - quaternary structure MSc. Biotechnology 1 st semester/ seminar session 2021

4. SECONDARY STRUCTURE Local spatial arrangement Dihedral angle, phi and psi Most prominent are α helix and β sheets Stable Consist of : - α - helix - β - pleated sheets - Non repetitive structures - Super secondary structures MSc. Biotechnology 1 st semester/ seminar session 2021 FIG. 6-4 Torsion angles of the polypeptide backbone ( Pg no : 134, Voet & Voet)

5. ALPHA HELIX Right handed Spiral structure Tightly packed, coiled Side chain extended outwards 3.6 residues per turn, 5.4 A ° pitch Phi- -57 ° & psi- -47 ° Hydrogen bond stabilizing factor, 3H bond per turn Ex α keratin , found in skin, hair and nails MSc. Biotechnology 1 st semester/ seminar session 2021 FIGURE 5–2 Orientation of the main chain atoms of a peptide about the axis of an α helix . Pg no : 103, Harpers illustrated Biochemistry

6. FIGURE 4–4 Models of the helix, showing different aspects of its structure. (a) Ball-and-stick model showing the intrachain hydrogen bonds. The repeat unit is a single turn of the helix, 3.6 residues. (b) The helix viewed from one end, looking down the longitudinal axis. (c) As this space-filling model shows, the atoms in the center of the helix are in very close contact. ( Pg no : 120, Leininger ) MSc. Biotechnology 1 st semester/ seminar session 2021

7. α - Keratin α - keratin is coiled coil ( Francis Crick & Linus Pauling ) Right handed helix Strength- mammals, hair, nail & etc intermediate filament(IF) Super twisted coiled coil-5.4 A ° Left handed hydrophobic residues Supramolecular complexes- intermediate filament of hair hardest & toughest α- keratin (Rhinoceros horn) MSc. Biotechnology 1 st semester/ seminar session 2021

8. BETA SHEETS 2/more polypeptides line up side by side Zig-zag arrangement of chain Β eta strand is extended H bond intra chain 2 residue per turn Stabilized by H bond between carbonyl & amide group R- group protrude from zig-zag in opposite direction Consist of - Parallel - Anti parallel MSc. Biotechnology 1 st semester/ seminar session 2021 FIG. 6-10 Pleated appearance of a 𝛃 sheet (Pg no: 139, Voet & Voet)

9. BETA SHEETS Parallel : -H bond chain extended in same direction - amino & carbonyl (same) Anti Parallel : -H bond extended in opp direction - amino & carbonyl (opp) Fig: 6.9 beta sheets ( Pg no : 138 Voet & voet) MSc. Biotechnology 1 st semester/ seminar session 2021

10. SUPER SECONDARY STRUCTURE Folding pattern of secondary structure (Motifs) βαβ motif β hairpin motif α α motif β barrel α β barrel Greek key motif MSc. Biotechnology 1 st semester/ seminar session 2021 FIG. 6-28 Schematic diagrams of super secondary structures. (a) βαβ motif, (b) β hairpin motif, (c) αα motif, and (d) Greek key motif, showing how it is constructed from a folded-over β hairpin. (Pg no: 151 Voet & Voet)

11. DOMAIN Jane Richardson Large polypeptide Binding of substrate Modular protein Combinations of super secondary elements Small globular protein MSc. Biotechnology 1 st semester/ seminar session 2021

12. CONCLUSION important roles in protein structure & protein folding used to predict tertiary structure determine the pattern of hydrogen bonding MSc. Biotechnology 1 st semester/ seminar session 2021

13. REFERENCE Voet & Voet , Fundamental of biochemistry 5 th edition. David L. Nelson & Michael M. Cox ,Principle of biochemistry, 6 th edition David A. Bender & Victor W ,Harpers illustrated biochemistry, 31 st edition MSc. Biotechnology 1 st semester/ seminar session 2021