Chapter 3 Protein Structures
Chapter 3 Protein Structures
Like the Greek sea god Proteus,who coud assume different forms.protelns act throu changesnon Proteins (from theGreek Protelos,Meaning "primary")are the primary agents of biologlcal fimction"Proteus,Old Man of the Sea Roman period masaic.from Thessalontka. Ist cntury A.D.Natlonal Archoeological Museum, Athens Anclent Art andd Architeture Collection Ld/Bridgeman An Library.London/New York)
Proteins are a diverse and abundant class of biomolecules,constituting more than 50%of the dry weight of cells.This diversity and abundance reflect the central role of proteins in virtually all aspects of cell structure and function.An extraordinary diversity of cellular activity is possible only because of the versatility inherent in proteins,each of which is specifically tailored to its biological role
Proteins are a diverse and abundant class of biomolecules, constituting more than 50% of the dry weight of cells. This diversity and abundance reflect the central role of proteins in virtually all aspects of cell structure and function. An extraordinary diversity of cellular activity is possible only because of the versatility inherent in proteins, each of which is specifically tailored to its biological role
Proteins have diverse functions: >Catalysts(Enzymes) >Provide structural rigidity >Control transport across membranes >Sensors and switches >Cause motion >Control gene function
Proteins have diverse functions: ➢Catalysts (Enzymes) ➢Provide structural rigidity ➢Control transport across membranes ➢Sensors and switches ➢Cause motion ➢Control gene function
Protein structure determines function >Proteins are single,unbranched chains of amino acid monomers >There are 20 different amino acids >A protein's amino acid sequence determines its three- dimensional structure(conformation) >In turn,a protein's structure determines the function of that protein >Four levels of structure determine the shape of proteins
Protein structure determines function ➢ Proteins are single, unbranched chains of amino acid monomers ➢ There are 20 different amino acids ➢ A protein’s amino acid sequence determines its threedimensional structure (conformation) ➢ In turn, a protein’s structure determines the function of that protein ➢ Four levels of structure determine the shape of proteins
Definitions of Protein Structure Primary structure-amino acid sequence Secondary structure-local conformation of peptide backbone Tertiary structure-interaction of different secondary structures on same polypeptide Quaternary structure-interaction of different polypeptides in structure that has more than one protein component
Definitions of Protein Structure Primary structure – amino acid sequence Secondary structure–local conformation of peptide backbone Tertiary structure– interaction of different secondary structures on same polypeptide Quaternary structure– interaction of different polypeptides in structure that has more than one protein component
窗 His Primary Secondary Tertiary Quaternary
Primary Secondary Tertiary Quaternary
3.1.Forces Influencing Protein Structure Hydrogen Bonds Hydrophobic Interactions Electrostatic Interactions Van der Waals Interaction
3.1 • Forces Influencing Protein Structure Hydrogen Bonds Hydrophobic Interactions Electrostatic Interactions Van der Waals Interaction
Non-bonding Forces Influencing Protein Structures Amino acids of a protein are joined by covalent bonding interactions.The polypeptide is folded in three dimension by non-bonding interactions.These interactions can easily be disrupted by extreme pH,temperature,denaturants,reducing reagents.We will discuss the nature of these types of forces H-bond interactions(12-30 kJ/mol) Hydrophobic Interactions(<40 kJ/mol) Electrostatic Interactions(20 kJ/mol) Van Der Waals Interactions(0.4-4 kJ/mol) The total inter-atomic force acting between two atoms is the sum of all the forces they exert on each other
Non-bonding Forces Influencing Protein Structures Amino acids of a protein are joined by covalent bonding interactions. The polypeptide is folded in three dimension by non-bonding interactions. These interactions can easily be disrupted by extreme pH, temperature, denaturants, reducing reagents. We will discuss the nature of these types of forces H-bond interactions (12-30 kJ/mol) Hydrophobic Interactions (<40 kJ/mol) Electrostatic Interactions (20 kJ/mol) Van Der Waals Interactions (0.4-4 kJ/mol) The total inter-atomic force acting between two atoms is the sum of all the forces they exert on each other
Hydrogen bonds H-bond describes a favorable interaction between a proton bonded to an electronegative atom and an atom carrying a lone pair of electrons: D-H +A D-HA Acceptors (A): Donors (D): This interaction is very important for maintaining protein backbone interactions
H-bond describes a favorable interaction between a proton bonded to an electronegative atom and an atom carrying a lone pair of electrons: D-H + A D H A Acceptors (A): Donors (D): This interaction is very important for maintaining protein backbone interactions Hydrogen bonds C N O O H O H O H N