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Fibrous Proteins

Fibrous Proteins. Examples. 1. a -keratins. Hair, nails, horns, skin. 2. Silk Fibroin. 3. Collagen. 4. Elastin. Saw Varsity’s a -keratins off. Amino Acid Composition of Fibrous Proteins. Collagen (Tendon).  -Keratin (Wool). Fibroin (Silk). Elastin (Aorta).

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Fibrous Proteins

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  1. Fibrous Proteins Examples 1. a-keratins Hair, nails, horns, skin 2. Silk Fibroin 3. Collagen 4. Elastin Saw Varsity’s a-keratins off

  2. Amino Acid Composition of Fibrous Proteins Collagen (Tendon) -Keratin (Wool) Fibroin (Silk) Elastin (Aorta) Gly 8.1 44.632.732.3 Ala 5.0 29.412.023.0 Ser 10.212.2 3.4 1.3 Glu + Gln 12.1 1.0 7.7 2.1 Cys 11.2 0 0 tr. Pro 7.5 0.3 22.1 10.7 Arg 7.2 0.5 5.0 0.6 Leu 6.9 0.5 2.1 5.1 Thr 6.5 0.9 1.6 1.6 Asp + Asn 6.0 1.3 4.5 0.9 Val 5.1 2.2 1.8 12.1 Tyr 4.2 5.2 0.4 1.7 Ile 2.8 0.7 0.9 1.9 Phe 2.5 0.5 1.2 3.2 His 0.7 0.2 0.3 tr. Met 0.5 0 0.7 tr. Trp 1.2 0.2 0 tr.

  3. -Keratin

  4. Keratin: an Intermediate Filament Protein What’s in Hair and Wool?

  5. Collagen Intramolecular Crosslinks b a’ Gly-X-Y a Left hand -helix X=Pro Y=HO-Pro Intermolecular Crosslinks Quarter Stagger

  6. ELASTIN Property of Resilience 4-way Stretch Aorta Lung Ligamentum Nuchae

  7. Alpha helix Beta structure Beta-alpha-beta Beta barrel Tertiary Structure Overall Shape (applies mainly to globular proteins) Structural Motifs

  8. a Helix Beta Sheet Turns or loops Packs Framework Globular Protein Molecules 3-Dominant Structural Features Typical Protein Connects

  9. Rules Governing Protein Folding Can we predict how a protein will fold on the basis of amino acid sequence data alone? 1. Globular Proteins have a defined outside and inside Hydrophobic buried inside Hydrophilic outside

  10. X Y Z Folding and Biological Activity Enzyme Active Site Z X Y Random Coil Folded Denatured Biologically Active

  11. TURNS (on Surfaces) Reverse direction abruptly Beta Bends or Turns (4 residues to execute sharp turn) H-bonding between carbonyl residue1 and amide N on residue 3. Glycine not in loop (Type I turn) Glycine in loop (Type II turn) Gamma (very tight turn) Proline in loop, bonding between 1 and 2 Tight Turn

  12. Reverse Turn in Polypeptides Glycine H-bond between 1 and 4 Twice more common than type 2

  13. Chou-Fasman Rule for Predicting Secondary Structure Propensity Helix Beta Sheet Beta Turn

  14. Protein Folding Mystery To fold a protein is negative entropy with respect to the protein. You go from a disordered to an ordered state. Folding is away from a natural tendency to exist in a random state? Where is the energy driving protein folding? ANSWER IN TEXTBOOK

  15. Folded Unfolded N N C C ANSWER ORGANIZED WATER DSTotal = DSsys - DSsurround

  16. QUATERNARY STRUCTURE Multisubunit Proteins SUBUNIT STRUCTURE HOMODIMER HETERODIMER

  17. WEAK FORCES IN PROTEIN

  18. hydrophobic hydrophilic Hydropathic Index + _

  19. Sum 1-9 (window) Sum 2-10 Sum 3-11 Sum 4-12 Sum 5-13 Sum 6-14 (-) (+) Determining Hydropathic Index

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