Module 1 Lesson 1 of 3-1.pdf
- 1. PROTEINS, DNA AND CHROMOSOMES MODULE 1 -Haymanti Bhanot, PhD
- 2. SHAPE AND STRUCTURE OF PROTEINS MODULE 1: LESSON 1 OF 3 BIOL6299 Fall 2022 Northeastern University (Source: Bruce Alberts; Alexander Johnson; Julian Lewis; David Morgan; Martin Raff; Keith Roberts; Peter Walter: 6th Edition)
- 3. INTRODUCTION • In this lesson we consider how the location of amino acids that form a specific protein can determine its shape and structural characteristics in the cell. • By the end of this lesson, you should be able to: • Identify common protein structures and domains. • Classify specific examples of important proteins and their cellular roles.
- 4. MODULE 1 – LESSON 1 OF 3 • Role of Proteins • Major components of Proteins • The Genetic Code • Amino acid side chains Protein Overview • Primary, Secondary, Tertiary and Quaternary Structure of Proteins • Protein Domains • Protein Folding • Disulfide bonds in Protein folding Common Protein Structure and Domains
- 5. PROTEIN OVERVIEW BIOL6299 Spring 2022 Northeastern University
- 6. THE ROLE OF PROTEINS Proteins serve as the building blocks of cells and execute virtually all the cells functions, like import and export of signals or small molecules. Proteins that carry the functions by which they conduct many of the necessary chemical reactions to drive cellular processes are referred to as enzymes.
- 7. THE MAJOR COMPONENTS OF PROTEINS • A protein molecule is made from a long chain of amino acids, that is joined to its neighbor molecule via covalent bond. • Each protein differs in its sequence and number of amino acids; therefore, it is the sequence of the chemically different side chains that make each protein distinct. • The function of a protein is dependent upon its structure, which is determined by the sequence of amino acids that make the protein.
- 8. THE MAJOR COMPONENTS OF PROTEINS • The two ends of a polypeptide chain are chemically different: one end carries the amino group (NH3+) known as the amino terminus, or N-terminus, and the other end carries the carboxyl group (COO-/COOH) known as the carboxyl terminus or C-terminus. • The amino acids sequence of a protein is always presented in the N-to-C terminus direction and is read from left to right.
- 9. THE GENETIC CODE • There are 20 amino acids found in proteins. • Each amino acid has a 3 letter code that corresponds to the nucleic acid sequence in mRNA, summarized in the figure. • The genetic code can be read by navigating from the left to right. • For e.g., First letter, Second letter, and the Third letter. • E.g.; let’s decode the codon CAU. v Genetic code is redundant.
- 10. POLARITY OF AMINO ACID SIDE CHAINS • There are equal number of polar and nonpolar side chains of amino acids; however, some side chains listed in this table as polar are large enough to have some nonpolar properties (for e.g., Try, Thr, Arg, Lys). • The polarity of the amino acid side chains that make up the polypeptide is an essential determinant of the final structure of protein.
- 11. POLARITY OF AMINO ACID SIDE CHAINS BASIC AMINO ACIDS CONTAIN SIDE CHAINS THAT CAN GAIN A PROTON.
- 12. POLARITY OF AMINO ACID SIDE CHAINS ACIDIC AMINO ACIDS CONTAIN SIDE CHAINS THAT CAN LOSE A PROTON.
- 13. UNCHARGED AMINO ACIDS CONTAIN SIDE CHAINS THAT HAVE NO CHARGE BUT HAVE POLAR CHARACTERISTICS AT NEUTRAL PH (FORM HYDROGEN BONDS WITH WATER). POLARITY OF AMINO ACID SIDE CHAINS
- 14. POLARITY OF AMINO ACID SIDE CHAINS NON-POLAR AMINO ACIDS CONTAIN SIDE CHAINS THAT ARE HYDROPHOBIC AND CAN CONTAIN RING- LIKE STRUCTURES.
- 15. COMMON PROTEIN STRUCTURES AND DOMAINS BIOL6299 Spring 2022 Northeastern University
- 16. FOUR LEVELS OF PROTEIN STRUCTURE Ø Primary Secondary Tertiary Quaternary
- 17. ALPHA HELICES Formed by backbone interactions parallel to the primary axis of helix. It is stabilized by hydrogen bonds between amide hydrogen of one amino acid and carbonyl oxygen four aminos acids away.
- 18. COILING FEATURES OF ALPHA HELICES – COILED-COIL E.g.: Alpha- Keratin Collagen Elastin
- 19. BETA SHEETS e.g: Fibronin Anti-parallel: folds back and forth on itself Parallel: neighboring polypeptide chains, run in same orientation Formed by hydrogen binding between adjacent parallel or anti-parallel peptide strands. In β-sheets, the backbone N–H and C=O of one strand hydrogen bond with the C=O and N–H of an adjacent strand, respectively.
- 20. ROLE OF PROTEIN DOMAINS *** A domain typically consists of between 40 and 350 amino acids, each with different functions.
- 21. SPECIFIC PROTEIN BINDING INTERACTIONS Head-to-Head Binding at different sites Noncovalent bonds of protein enable it to bind to other proteins which generates larger structures in the cell.
- 22. IMPORTANCE OF PROTEIN FOLDING • An important feature governing the folding of any protein is the distribution of its polar and nonpolar amino acids. • The nonpolar amino acid side chains are hidden inside of the protein to form a tightly packed hydrophobic core of atoms that are protected from water that surrounds the cell. • The polar amino acid side chains tend to gather on the outside of the protein, where they can interact with water and other polar molecules in the cell’s environment.
- 23. PROTEINS FOLD INTO THE LOWEST ENERGY CONFIRMATION ***MOLECULAR CHAPERONS: Conversely, many proteins use special helper proteins to aid in protein folding. These molecular chaperons are often necessary to prevent aggregation of proteins that have temporarily exposed hydrophobic regions, especially in newly synthesized proteins.
- 25. ASSEMBLY FACTORS OF PROTEINS Insulin: synthesized as proinsulin, a larger protein. cannot spontaneously re-construct itself if di-sulfide bonds are disrupted.
- 26. IN THIS LESSON • Identified the common protein structures and domains • Classified specific examples of important proteins and their cellular roles.