Post on 05-Apr-2018
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Part IHierarchical Structure of Proteins
Protein Structure and FunctionChap. 3
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Primary Structure
N-term. C-term.
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Secondary Structure-alpha ( a ) helix
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Secondary Structure-beta ( ) sheet
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Tertiary Structure
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Motifs-Regular Combinations of Secondary Structure
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Motifs-Regular Combinations of Secondary Structure
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Motifs-Regular Combinations of Secondary Structure
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Protein Domains
3° Structureof HA
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Modular Nature of Proteins
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Quaternary Structure of Proteins
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Macromolecular Assemblies
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Transcription Initiation Machinery
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Conservation of Protein Structure andFunction Throughout Evolution
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Structural Similarities of the Different Globins
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Part II
Folding, Modification, andDegradation of Proteins
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Molecular Chaperone-Mediated Protein Folding
1. ATP-bound Hsp70 binds to unfolded protein
2. Hydrolysis of ATP to ADP (release of P i) promotes folding
3. Exchange of ATP for ADP releases folded protein
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Chaperonin Mediated Protein Folding
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Chemical Modification of Amino Acid Residues
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Chemical Modification of Amino Acid Residues
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Protein Degradation-Protein Life span varies from a few minutes to the life of the cell
-Several pathways for degradation of proteins
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Protein Degradation-Protein Life span varies from a few minutes to the life of the cell
-Several pathways for degradation of proteins1. Lysosomal-membrane bound organelle
-Interior is highly acidic and containshydrolytic enzymes
-Primarily degrade extracellular proteins takenup by the cell
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Pathways for Lysosomal Degradation of Proteins
Fig. 5-20
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Protein Degradation-Protein Life span varies from a few minutes to the life of the cell
-Several pathways for degradation of proteins1. Lysosomal-membrane bound organelle
-Interior is highly acidic and containshydrolytic enzymes
-Primarily degrade extracellular proteins takenup by the cell
2. Proteasome-directed degradation-Macromolecular machinethat degrades proteins than have been poly-ubiquitinated
-Ubiquitin-76 amino acid polypeptide that is covalentely
attached to lysine residues-Polyubiquitin chain is recognized by the proteasome-Degrades proteins in an ATP-dependent manner intoshort (7-8 amino acid) peptides
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Ubiquitination and Proteasome-mediated Protein Degradation
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Part III
Enzymes and Chemical Work of Cells
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Antibody-Antigen Interactions are Highly Specific
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Antibody-Antigen Interactions are Highly Specific
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Enzymes
-Catalyze chemical alteration of their ligands
-Ligand=Substrate-Most chemical reactions in the cell are catalyzed byenzymes
-Enzymes do not alter the reaction
-Enzymes increase the reaction rate by lowering the
activation energyi.e.-accelerate the formation of products fromreactants without altering the value of G
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G
Enzymes Accelerate the Reaction Rate
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Enzyme Active Site Binds the Substrate
Kinase Core-240 Amino aciddomain of PKA
Protein Kinase A(PKA)
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No Substrate bound Substrate binding causesconformational change tobring ATP and peptidebinding sites closer together
Conformational Change Caused by Substrate Binding
E Ki i
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Enzyme Kinetics-Conversion of one substrate into a product using two differentenzyme concentrations and increasing substrate concentrations
E Ki i
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Enzyme Kinetics-Conversion of one substrate into a product using constant enzymeconcentration and two substrates
-Enzyme has different affinity for the two substrates
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Enzymes in Common Pathways
Diffusion of product to nextenzyme in the pathway
Scaffold-keepsenzymes closeto each other
Multifunctional Enzyme-enzymeencoded by a single gene that hasmore than one catalytic activity
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Pyruvate Dehydrogenase Complex
P IV
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Part IV
Mechanisms for RegulatingProtein Function
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Cooperative Binding of O 2 to Hemoglobin
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Ligand Binding Activates Protein Kinase A Catalytic Subunit
l d l 2+ d h
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Calmodulin Functions as Ca 2+ Binding Switch Protein
GTP Bi di P t i F ti M l l S it h
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GTP-Binding Proteins Function as Molecular Switches
Regulation of Protein Function by Phosphorylation/Dephosphorylation