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STRUCTURE OF PROTEIN

STRUCTURE OF PROTEIN. Prepared by- Parikha Srivastav (P.G.T CHEM.) K.V. BALRAMPUR. Structure of Protein.

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STRUCTURE OF PROTEIN

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  1. STRUCTURE OF PROTEIN Prepared by- Parikha Srivastav (P.G.T CHEM.) K.V. BALRAMPUR

  2. Structure of Protein • Proteins are fundamental components of all living cells, performing a variety of biological tasks. • Proteins are macromolecules and have four different levels of structure:– primary, secondary, tertiary and quaternary.

  3. There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids, contain both a basic amino group and an acidic carboxyl group. This functionality allows the individual amino acids to join together in long chains by forming peptide bonds amide bonds between the -NH2 of one amino acid and the -COOH of another. Sequences with fewer than 50 amino acids are generally referred to as peptides, while the terms protein or polypeptide are used for longer sequences. A protein can be made up of one or more polypeptide molecules.

  4. R NH3+ C COO- H Amino acid: Basic unit of protein Different side chains, R,determine the properties of 20 amino acids. Carboxylic acid group Amino group An Amino acid

  5. The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical and structural properties to the final peptide or protein. • Each amino acid has both a one-letter and three-letter abbreviation. These abbreviations are commonly used to simplify the written sequence of a peptide or protein.

  6. Types Of Amino Acid

  7. Classification Depending on the side-chain substituent, an amino acid can be classified as:- • Acidic • Basic • Neutral

  8. O O Alanine Cysteine C H2N C H2N OH OH Generic C C H H H H C C O Amine Acid H HS H H Non-polar C Polar H2N OH C O O Aspartic acid ? Histidine R H C H2N C H2N OH OH C C H H H H C C O C H H Basic C Acid OH NH C C H+N Different Amino Acid

  9. Hierarchical structure • Primary structure (AMINO ACID SEQUENCE) • Secondary structure ( helix, sheet) • Tertiary structure (three dimensional structure formed by assembly structures) • Quaternary structure (structure formed by more than one polypeptide chains)

  10. Primary Structure The sequence of amino acids in the primary structure determines the folding of the molecule. Met-Gly-Ala-Pro-His-Ile-Asp-Glu-Met-Ser-Thr-..................

  11. PRIMARY STRUCTURE .

  12. Secondary Structure • The two main types • α-helix • ß-sheet

  13. -helix The α-helix is a right-handed coiled strand. The side-chain substituents of the amino acid groups in an α-helix extend to the outside. Hydrogen bonds form between the oxygen of the C=O of each peptide bond in the strand and the hydrogen of the N-H group of the peptide bond four amino acids below it in the helix. The hydrogen bonds make this structure especially stable. The side-chain substituents of the amino acids fit in beside the N-H groups.

  14. H N C H C H + N O C C N H O - C C N H H O O O C H N C N C OH C H O C C N H H H C H H C C C O N H H HO H H C C N C O O Protein Secondary StructureHelix

  15. ß-sheet The hydrogen bonding in a ß-sheet is between strands (inter-strand) rather than within strands (intra-strand). The sheet conformation consists of pairs of strands lying side-by-side. The carbonyl oxygen in one strand hydrogen bond with the amino hydrogen's of the adjacent strand. The two strands can be either parallel or anti-parallel depending on whether the strand directions (N-terminus to C-terminus) are the same or opposite.

  16. O O O O O O O O H H H H H H H H C C C C C C C C N N N N N N N N C C C C C C C C C C C C C C C C C C C C C C C C N N N N N N N N H H H H H H H H O O O O O O O O O O O O H H H H N N N N C C C C C C C C C C C C N N N N C C C C H H H H O O O O Protein Secondary Structure:b Pleated Sheet

  17. Tertiary Structure • The overall three-dimensional shape of an entire protein molecule is the tertiary structure. • The protein molecule will bend and twist in such a way as to achieve maximum stability or lowest energy state.

  18. Tertiary Structure R-group interactions: • Weak: • sulphide linkage • hydrogen bonds • ionic bonds • hydrophobic interactions • Strong: • disulfide bridge

  19. Quaternary Structure • The quaternary structure refers to how these protein subunits interact with each other and arrange themselves to form a larger aggregate protein complex. • The final shape of the protein complex is once again stabilized by various interactions, including hydrogen-bonding, disulphide-bridges and electrostatic interactions.

  20. Quaternary Structure • Two or more polypeptides folding together

  21. ASSIGNMENTAn optically active amino acid (A) can exist in threeformsdepending on the pH of the medium if the molecular formula of A is C3H7NO2write-Structure of compound in aquous medium. What are such ions called?In which medium the cationic form of compound A exist?In alkaline medium ,toward which electrode will the compound. A migrate in electric field?

  22. The four levels of protein structure

  23. THANK YOU

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