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Chapter 5 Protein Function Copyright © 2011 by John Wiley & Sons, Inc. Charlotte W. Pratt | Kathleen Cornely Essential Biochemistry Second Edition
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N-terminus C-terminus
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F8 His
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Y = Fractional Saturation (Y=1 for 100% saturation) p 50 = 2.8 torr
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Mb α β
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Amino Acid Sequences of Mb and Hb Residues identical in α and β subunits Residues identicl in all 3 Residues invariant in all vertebrates
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Globin evolution
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Mb Hb p 50 Hb = 26 torr p 50 Mb = 2.8 torr
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Hb confomation changes upon oxygenation/deoxygenation
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Figure 7-5
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DeoxyHb OxyHb
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Figure 10-16Triggering mechanism for the T R transition in Hb. Page 333
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Subunit interactions change deoxygenation (b) deoxygenation oxygenation
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Figure 10-17The 1 C– 2 FG interface of Hb in (a) the T state and (b) the R state. Page 334
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Figure 10-18The hemoglobin 1 2 interface as viewed perpendicularly to Fig. 10-13. Page 335
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Box 7-3
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Figure 7-15
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Figure 7-16
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Table 7-1
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A map indicating the regions of the world where malaria caused by P. falciparum was prevalent before 1930. Page 184
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Linus Pauling noted that sHb had a different charge than normal Hb. Single point mutation at position A3 in the β subunit: Glu →Val!!!
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Figure 7-19
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SHb polymers
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Figure 7-18b
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Tissue Lungs
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Figure 10-7Comparison of the O 2 - dissociation curves of “stripped” Hb and whole blood in 0.01M NaCl at pH 7.0. Page 326
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Binding and Release of: O 2, BPG, CO 2, H + 4O 2 + Hb-BPG-CO 2 -H + Hb-(O 2 ) 4 + BPG + CO 2 +H + BPG + CO 2 +H + + Hb-(O 2 ) 4 Hb-BPG-CO 2 -H + + 4O 2 Lungs: Capillaries: Respiring cells: O 2 +MbMb-O 2 Mitochondrion(O 2 ) + Mb CO 2
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Binding of BPG to deoxyHb.
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The effects of BPG and CO 2, both separately and combined, on hemoglobin’s O 2 -dissociation curve compared with that of whole blood (red curve).
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Fibrous proteins Actin and Tubulin
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Actin monomer ATP ATP is hydrolyzed to ADP to drive the polymerization reaction
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F-actin (not G-actin catalyze ATP hydrolysis
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Polymerization is reversible
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Microfilaments help cells move
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β-Tubulin Tubulin αβ dimer with bound G
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Assembly of a microtubule
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Tubulin depolymerization Protofilaments curve away from the microtubule and separate before dimers dissociate
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Microtubules in a dividing cell!
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Product of the meadow saffron plant causes microtubules to depolymerize and therefore blocks cell division!
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Originally from the endangered Pacific yew tree Binds β tubulin in a microtubule but not to free tubulin preventing depolymerization and thus cell division. Toxic to rapidly dividing cells.
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SEM of Human skin!!!
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Keratin forms a coil-coil structure.
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HAIR
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Collagen
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Collagen: mostly (Gly-Pro-Hyp) n
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Narrow lh helix Pro Hyp Gly
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Collagen triple helix
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Cross-linking of collagen fibers Cross-linking increases with age—skin is less plastic
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A CHILD with a collagen defect Osteogenisis imperfecta
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Myosin
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Thick filaments of Myosin
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