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

2. STRUCTURE OF PROTEIN Proteins are fundamental components of all living cells, performing a variety of biological tasks. 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. 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. 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. 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. 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. AMINO ACID: BASIC UNIT OF PROTEIN COO - NH 3 + C R H An Amino acid Different side chains, R,determine the properties of 20 amino acids. Amino group Carboxylic acid group

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. 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. 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 Acidic Basic Basic Neutral Neutral

8. Polar Basic Acid ? Amine DIFFERENT AMINO ACID OH O H H2NH2N C C R Generic Non-polar C C C OH H H O H+NH+N H H2NH2N C NH C C Histidine H H2NH2N C C H H O OH O C C Aspartic acid C C C OH H H O HS H H2NH2N Cysteine OH H H O H H H2NH2N C C C Alanine

9. HIERARCHICAL STRUCTURE

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 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. 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. The hydrogen bonds make this structure especially stable. The side-chain substituents of the amino acids fit in beside the N-H groups.

14. + - PROTEIN SECONDARY STRUCTURE  HELIX C O OHCN H H H C HOH C H O CN H H H C HH C H N C O C H N O C C O C H N C H N C O C O C O C O C H N H N C H N

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 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 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. 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. PROTEIN SECONDARY STRUCTURE: B PLEATED SHEET N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O N H C O C H C C N O

17. TERTIARY STRUCTURE The overall three-dimensional shape of an entire protein molecule is the 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. 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: Weak: sulphide linkage sulphide linkage hydrogen bonds hydrogen bonds ionic bonds ionic bonds hydrophobic interactions hydrophobic interactions Strong: Strong: disulfide bridge 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 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. 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 Two or more polypeptides folding together

21. ASSIGNMENT An optically active amino acid (A) can exist in threeforms depending on the pH of the medium if the molecular formula of A is C 3 H 7 NO 2 write- 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