Quaternary structure of protein By KK Sahu Sir

INTRODUCTION
DEFINATION
HISTORY
TYPES OF PROTIEN STRUCTURE
PRIMARY STRUCTURE
SECONDARY STRUCTURE
TERTIORY STRUCTURE
QUATERNARY STRUCTURE
FORCE INVOLVE IN QUATERNARY STRUCTURE
EXAMPLES OF QUATERNARY STRUCTURE
CONCLUSIONS
REFERENCES

1. QUATERNARY STRUCTURE OF PROTEIN By KAUSHAL KUMAR SAHU Assistant Professor (Ad Hoc) Department of Biotechnology Govt. Digvijay Autonomous P. G. College Raj-Nandgaon ( C. G. )

2. SYNOPSIS INTRODUCTION DEFINATION HISTORY TYPES OF PROTIEN STRUCTURE PRIMARY STRUCTURE SECONDARY STRUCTURE TERTIORY STRUCTURE QUATERNARY STRUCTURE FORCE INVOLVE IN QUATERNARY STRUCTURE EXAMPLES OF QUATERNARY STRUCTURE CONCLUSIONS REFERENCES

3. INTRODUCTION The quaternary protein structure involves the clustering of several individual peptide or protein chains into a final specific shape. A variety of bonding interactions including hydrogen bonding, salt bridges, and disulfide bonds hold the various chains into a particular geometry.

4. DEFINATION Quaternary structure is the arrangement of multiple subunits or peptide chains. Proteins are fundamental components of all living cells, performing a variety of biological tasks. Each protein has a particular 3D structure that determines its function.

5. HISTORY 1930-50’s –Pauling & Corey studied the peptide bond & predicted 2 structure (a-helix & b-sheet) 1954 Nobel Prize in Chemistry • 1953 –Frederick Sanger determined the sequence of insulin; 1stprotein sequence known 1958 Nobel Prize in Chemistry •1950’s Christian Anfinsen showed that the AA sequence determines the structure of a protein 1972 Nobel Prize in Chemistry •1958 –John Kendrew solved the structure of myoglobin 1962 Nobel Prize in Chemistry

6. TYPES OF PROTEIN STRUCTURE Primary ( 1) –order of amino acids • Secondary (2o) –spatial arrangement of the polypeptide backbone (AA’s close in close proximity) • Tertiary (3o) –overall structure of entire polypeptide (AA’s far apart) • Quaternary (4o) –arrangement of subunits; only for proteins with 2+ polypeptide chains

7. PRIMARY STRUCTURE The primary structure  refers to amino acid linear sequence of the polypeptide chain. The primary structure is held together by covalent bonds such as peptide bonds, which are made during the process of  protein biosynthesis or translation.

8. SECONDARY STRUCTURE Secondary structure refers to highly regular local sub-structures. Two main types of secondary structure, the alpha helix and the beta strand or  beta sheets, were suggested.

9. Alpha helix and beta sheet

10. TERTIARY STRUCTURE Tertiary structure refers to three-dimensional structure of a single protein molecule. The alpha-helices and beta-sheets are folded into a compact globule.

11. QUATERNARY STRUCTURE: Quaternary structure is the three-dimensional structure of a multi-subunit protein. the quaternary structure is stabilized by the same non-covalent interactions and disulfide bonds as the tertiary structure . Complexes of two or more polypeptides are called multimers.

12. PROTIEN LEVELS

13. FORCES INVOLVE IN QUATERNARY STRUCTURE Disulfide Bonds: Hydrogen Bonding: Non-Polar Hydrophobic Interactions: Protien-protien interaction: Peptide bond

14. Disulphide bond

15. Hydrogen bonding

16. Hydrophobic interaction

17. PROTEIN-PROTEIN INTERACTION Proteins are capable of forming very tight complexes. For example, ribonuclease inhibitor binds to ribonuclease A with a roughly dissociation constant. Other proteins have evolved to bind specifically to unusual moieties on another protein, e.g., biotin groups (avidin), phosphorylated tyrosines (SH2 domains) or proline-rich segments (SH3 domains).

18. Peptide bond

19. TYPES OF QUATERNARY PROTEIN 1 FIBROUS 2 GLOBULAR FIBROUS PROTEIN- The final beta-pleated sheet structure of silk is the result of the interaction of many individual protein chains. Specifically, hydrogen bonding on amide groups on different chains is the basis of beta-pleated sheet in silk proteins.

20. FIBROIN

21. Silk protein

22. GLOBULAR PROTEIN- globular proteins may have a combination of the above types of structures and are mostly clumped into a shape of a ball. Have compact 3-D structures More common in the cell than fibrous proteins Ex. Myoglobin (Mb), hemoglobin (Hb), antibodies, CD4 cell-surface protein, ribonuclease, PRP protein, enzymes,

23. EXAMPLES OF GLOBULAR STRUCTURE HAEMOGLOBIN-

24. Haemoglobin is found in red blood cells The haemoglobin molecule is a tetramer consisting of 4 polypeptide chains, known as globins, which are usually: 2 alpha chains that are each 141 amino acids long 2 beta chains that are each 146 amino acids long Attached to each chain is an iron-containing molecule known as haem

25. INSULIN

26. Human insulin contains two protein chains with a total of 51 amino acids. The chains are connected by two disulfide bonds. Insulin is classified as a hormone and is needed for the proper utilization of glucose Diabetics must take insulin injections to maintain health.

27. CONCLUSIONS Proteins serve a variety of functions within cells. Some are involved in structural support and movement, others in enzymatic activity, and still others in interaction with the outside world. Indeed, the functions of individual proteins are as varied as their unique amino acid sequences and complex three-dimensional physical structures.

28. REFERENCES: http://www.nature.com/ http://www.elmhurst.edu Principles of Biochemistry, Nelson and Cox,4 th edition