Chapter 5 Structure and Function of Protein
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Transcript of Chapter 5 Structure and Function of Protein
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Chapter 5
Structure and Function of Protein
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1. Amino acids
COO-NH3+ C
R
H
R--Different side chains, determin the properties of 20 amino acids.
Amino group Carboxylic acid group
structure
5.1 Protein Components
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Aliphatic Aromatic Sulfur containing
Polar/uncharged basic/acidic
Hydrophobic- water fearing. non-polar side chains
Hydrophilic- water loving. polar, neutral chains negatively charged, positively charged
Classification
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polypep
tide
protein
oligopeptid
e
dipeptide
tripeptide
decapeptid
e
3. Peptide and Polypeptide
2. Peptide bond Peptide Plane
Dihedral angle
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5.2 Protein Structure
1. Primary structure
----linear sequence of amino acids in a
polypeptide chain
2. Secondary structure -helix
-strand, -sheet, -barrel, -turn
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3. Tertiary Structure
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Hemoglobin - an example of a four-subunit protein
4. Quaternary Structure
Animation
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5. Bonds and Forces for Protein Structu
re
◆ Covalent bond
◆ Electrostatic interactions
◆ van der Waals interactions
◆ Hydrogen bonds
◆ Hydrophobic interactions
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6. Denaturation and Renaturation of Prote
in
denaturat
ion
renaturat
ion
active inactive active
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Animation
5.3 Protein Folding
1. Concept
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Forces Involved in the Protein Foldi
ng
◆ Electrostatic interactions
◆ van der Waals interactions
◆ Hydrogen bonds
◆ Hydrophobic interactions
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3. Models for Protein Folding
◆ Framework Model
◆ Hydrophobic Collapse Model
◆ Nuclear-Condensation Model
◆ Diffusion-Collision model
◆ Funnel or Energy-landsape models
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DISEASEPROTEIN AFFECTED
MOLECULAR DEFECT
Cystic FibrosisCystic fibrosis transmembrane regulator (CFTR)
Misfolding and retention in the endoplamic reticulum, leading to degradation
Marfan Syndrome
Fibrillin Misfolding
NephrogenicDiabetesInsipidus
Vasopressin receptor or aquaporin water channel
Misfolding and retention in theendoplasmic reticulum
α-1-Antitrypsin Deficiency
Alpha-1-AntitrypsinMisfolding and retentionin the endoplasmic reticulum, leading toaggregation in cells of synthesis
Creutzfeldt-Jakob Disease
Prion proteinAggregation in brain (after protein release)
Alzheimers's Disease
Beta-amyloidAggregation in brain (after protein release)
5. Protein Misfolding and Diseases
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5.4 Structure and Function of Enzyme
Most enzymes are proteins
J.B.Sumner J.H.Northrop
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2. Classification of enzymes
Based on type of reaction
Oxidoreductase catalyze a redox reaction
Transferase transfer a functional group
Hydrolase cause hydrolysis reactions
Lyase break C-O,C-C or C-N bonds
Isomerase rearrange functional groups
Ligase join two molecules
1. Proteins play key roles in a living system
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3. Structure of Enzyme
(1) Active site Catalytic site Binding site
(2) Specificity Group specificity Absolute specificity Stereo specificity Sequence specificity
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4. Catalysis Mechanism
(1) Hypothesis/Theory
Lock and key model
Induced-fit model
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Lock and key Theory
( 锁钥学说 )
Hermann Emil FischerThe Nobel Prize in Chemistry 1902
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Induced –fit hypotheory
( 诱导契合假说 ) 1958
(1998 Albert Lasker Award )
Daniel KoshlandProfessor, Biochemistry and Molecular Biology, University of California, Berkeley
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Induced-Fit Model of enzyme catalysis
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(3) Features of catalytic reaction ▼high efficiency ▼specificity ▼be regulated ▼inactive easily
(4) Factors affecting enzyme activity Temperature pH Substrate concentration Enzyme concentration
(2) Steps in an enzymatic reaction
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Summary
1. Peptide, polypeptide
2. Hierarchical protein structure.
3. Motifs and Domains of protein
4. Protein folding, misfolding and diseases
5. Protein functions and classification
6. Structure of enzyme and its specificity
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