Structure and function of protein

A presentation on structure and function of protein
And short animation vedio

1. A presentation on Structure and function of Protein Presented by: Mujeeb Ur Rehman Presented to : Dr Abid Jan Course: Molecular Biology Department: Biotechnology and Genetic Engineering Semester: 3 rd 1/15/2020 1 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

2. Contents Introduction Amino Acids Structure of Amino Acids Classification of Amino Acids by R group Structural organization of protein Interactions b/w the structure of Protein Functions of Protein 1/15/2020 2 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

3. Introduction Proteins are the most abundant organic molecules of the living system. They constitute about 50% of the dry weight. They constitute the fundamental basis of structure and function of life. In 1839,Dutch Chemist GJ. Mulder was first to describe about the proteins. The term protein is derived from the Greek word “ proteios ”, meaning first place. There are approximately 75,000 polypeptide in humans. 1/15/2020 3 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

4. Amino Acid Amino acids are a group of organic compounds containng two functional groups- amino and carboxyl. The amino group [-NH2] is basic while the carboxyl group [-COOH] is acidic in nature. There are about 300 aminoacids occurs in nature. Only twenty (20) of them are standard amino acids. 1/15/2020 4 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

5. Amino acids contid …. Amino acids are devided into two groups I,e Standard and non-standard amino acids Satandard Amino Acids: All those amino acids which take part in protein synthesis are called standard amino acids . Non-Standard amino acids: are those amino acids which do not take part in protein synthesis , They are present freely in the cells . 1/15/2020 5 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

6. Amino acids contid … Standard amino acids are further classified into three types I,e Essential ,Non essential and conditional amino acids. Essential amino acids are those amino acids which are synthesized by our body in inadequate amount .(  histidine , isoleucine, leucine , lysine, methionine, phenylalanine, threonine,  tryptphan and valine ). Non essential amino acids are those amino acids which are synthesized by our body in adequate/ suffeicient amount.(alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline , serine, and tyrosine). 1/15/2020 6 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

7. Amino acids contid … Conditional Amino acids are those amino acids which are not essential except in time of illness,pregnacy and lactation.( arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline , and serine). Each amino acids has 4 different groups attached to α – carbon (which is C atom next to COOH).These 4 groups are; amino group, COOH group, Hydrogen atom and side chain(R). Figure 1 ( Amino Acid) Figure 1 (Amino acid) 1/15/2020 7 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

8. Amino Acids Chart 1/15/2020 8 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

9. Classification of Amino Acids by R group The amino acids are classified into five main classes based on the properties of their R groups. These are: Non-polar, Aliphatic R Group Aromatic R Group Polar, Uncharged R Group Positively Charged R Group Negatively Charged R group There are 20 different types of amino acids. 1/15/2020 9 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

10. NON-POLAR ALIPHATIC R GROUP 1/15/2020 10 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

11. AROMATIC R GROUP 1/15/2020 11 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

12. POLAR ,UNCHARGED R GROUP 1/15/2020 12 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

13. POSITIVELY CHARGED R GROUP (BASIC) 1/15/2020 13 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

14. NEGATIVLY CHARGED R GROUP (ACIDIC) 1/15/2020 14 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

15. Structural organization of protein   The structural and functional features of proteins and protein complexes are addressed at four levels of hierarchal organization. These are: Primary structure (1º-Structure) Secondary Structure (2º-Structure) Tertiary Structure (3º-Structure) Quaternary Structure (4º-Structure) 1/15/2020 15 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

16. Continued…. Primary Structure: The primary structure of protein refers to the sequence of amino acids present in the polypeptide chain.  Amino acids are covalently linked by peptide bonds or covalent bonds. Each component amino acid in a polypeptide is called a "residue” or “moiety”. By convention the primary structure of protein starts from the amino terminal (N) end and ends in the carboxyl terminal (C) end. 1/15/2020 16 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

17. Continued…. Secondary Structure: Secondary Structure  refers to the coiling or folding of a polypeptide chain that gives the protein its 3-D shape. Results from hydrogen bonds at regular intervals along the polypeptide backbone. There are two types of secondary structures observed in proteins. One type is the  alpha (α) helix  structure. This structure resembles a coiled spring and is secured by hydrogen bonding in the polypeptide chain.  The second type of secondary structure in proteins is the  beta (β) pleated sheet .  This structure appears to be folded or pleated and is held together by hydrogen bonding between polypeptide units of the folded chain that lie adjacent to one another. 1/15/2020 17 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

18. Continued…. Tertiary structure: T ertiary Structure  refers to the comprehensive 3-D structure of the polypeptide chain of a  protein . There are several types of bonds and forces that hold a protein in its tertiary structure.  1/15/2020 18 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

19. Covalent bonds stabilizing protein structure Proteins are stabilized by two types of covalent bonds: 1. Peptide bonds 2. Disulphide bonds. Peptide bonds : Formation of peptide bond = a covalent bond is formed by amide linkage between the carboxyl group of one amino acid and amino group of another amino acid by removal of a water molecule. Disulfide bonds : Covalent bonds stabilizing proteins structure. Cysteine : with functional group -SH ( sulfhydryl ) Cystine : functional group -S-S-(disulphide A covalent disulfide (-S-S)bond formed between the sulfhydryl group (-SH)of two Cysteine residues in the same or different polypeptide chains.  These disulfide bonds contribute to structural conformation and stability of proteins . 1/15/2020 19 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

20. Role of Cysteine and Cystine in formation Covalent bonds stabilizing protein structure  Cystine has disulfide (S-S) as a functional group . It is formed from Cystine ( Dicysteine )after oxidation. Cystine on reduction yields two Cysteine molecules. Two Cysteine residues can connect two polypeptide chains by formation of Interchain disulfide bonds or links . e.g. Keratin , Insulin. 1/15/2020 20 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

21. Non covalent interactions in tertiary structure Tertiary structure of proteins :refers to the three-dimensional conformation of proteins generated and maintained by weak bonds(valence forces) / non-covalent interactions such as:    a. Hydrogen bonds : formed between -CO and NH- of two different peptide bonds or -OH group of hydroxy amino acids(Serine etc.) and-COOH groups of acidic amino acids Aspartic or Glutamic acid. b. Ionic bonds/electrostatic interactions/salt bridges : formed between oppositely charged groups when they are in close vicinity . They are also formed oppositely charged R groups of polar amino acid residues . e.g. basic ( Histidine , Arginine , Lysine)and acidic amino acids (Aspartic acid, Glutamic acid) . 1/15/2020 21 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

22. c. Hydrophilic interactions :  water loving groups are associated with water. d. Hydrophobic interactions : formed between hydrophobic groups (hydrocarbon like)of amino acids like Alanine and Phenylalanine. e. Van der Waal forces :  1/15/2020 22 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

23. c. Hydrophilic interactions :  water loving groups are associated with water. d. Hydrophobic interactions : formed between hydrophobic groups (hydrocarbon like)of amino acids like Alanine and Phenylalanine. e. Van der Waal forces :  weak ,but collectively contribute maximum towards the protein structure. During folding of globular proteins (spherical/round), hydrophobic groups prefer to be interior and Hydrophilic groups prefer to be on the surface of protein molecule. The tertiary structure acquired by a native protein is always thermodynamically most stable. 1/15/2020 23 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

24. Weak bonds stabilizing tertiary structure of proteins 1/15/2020 24 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

25. Quaternary structure:   refers to the structure of a protein macromolecule formed by interactions between multiple polypeptide chains. Each polypeptide chain is referred to as a subunit. Proteins with quaternary structure may consist of more than one of the same type of protein subunit.  They may also be composed of different subunits.  Hemoglobin is an example of a protein with quaternary structure. Hemoglobin, found in the blood ,is an iron-containing protein that binds oxygen molecules. It contains four subunits: two alpha subunits and two beta subunits. 1/15/2020 25 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

26. Interaction invoved in the quaternary structure of protein Forces involved in quaternary structure Hydrogen bonds Ionic /electrostatic interactions Hydrophobic interactions Van der Waal forces The same weak bonds are involved in secondary and tertiary structure in this associations. Quatarnary structure stabilize by above four mentioned bonds. 1/15/2020 26 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

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28. Four Level Of Structural Organization of proteins 1/15/2020 28 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

29. Functions of protein ANTIBODIES: are specialized proteins involved in defending the body from antigens (foreign invaders). One way antibodies destroy antigens is by immobilizing them so that they can be destroyed by white blood cells. 1/15/2020 29 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

30. FUNCTION CONTI… ENZYMES: are proteins that facilitate biochemical reactions. They are often referred to as catalysts because they speed up chemical reactions. Examples include the enzymes lactase and pepsin. Lactase breaks down the sugar lactose found in milk. Pepsin is a digestive enzyme that works in the stomach to break down proteins in food. HORMONAL PROTEINS: are messenger proteins which help to coordinate certain bodily activities. Examples include insulin and oxytocin . Insulin regulates glucose metabolism by controlling the blood-sugar concentration. Oxytocin stimulates contractions in females during childbirth. are responsible for movement. Examples include actin and myosin. These proteins are involved in muscle contraction and movement. 1/15/2020 30 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

31. CONTRACTILE PROTEIN : Are responsible for movement, Examples include ACTIN and MYOSIN. These protein are involved in muscle contraction and movement. Transport Proteins: are carrier proteins which move molecules from one place to another around the body. Examples include hemoglobin and cytochromes . Hemoglobin transports oxygen through the blood. Cytochromes operate in the electron transport chain as electron carrier proteins. 1/15/2020 31 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST.

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33. That’s All 1/15/2020 33 Molecular biology .Department of Biotechnology and genetic Engineering ,KUST. Thank you …