lecture_17legge - Example of each level of protein...

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1 Exam II Review (10 / 21 / 2008) TOPICS Protein Structure Myoglobin/Hemoglobin Enzymes Enzyme Kinetics Example of each level of protein structure Fibrous Proteins Nails, hair, horns and feathers α or β -forms 30 variants, tissue specific type I and type II acidic negative charge basic positive charge α keratin hair- 20 μ M diameter macrofibril 2000 Å parallel to hair microfibril 80 Å and high sulfur content protein can break -S-S- with mercaptans and reconnect (i.e. can give hair a “permanent” wave) α Keratin - A Coiled Coil α keratin proteins are helical but spacing differs from a regular α -helix a 5.1 Å vs. 5.4 Å pitch. This change in pitch forms closely associated pairs of helices. Each pair consists of a type I and type II protein Left-handed coil coiled-coil 310 AA residues 7-residue pseudo repeat. Helical wheel - 3.6 residues/turn 360 ° = 100 ° per residue a - b - c - d - e - f - g - a repeat on side of helix ↑↑ Helical wheel diagram a and d residues are nonpolar. View down the coil axis Collagen triple residue repeat: Gly-X-Y X often Pro Y often Hyp like a poly Gly or poly Pro helix Left-handed 3.0 residues/turn pitch 9.4 ° extended conformation the prolines avoid each other. 3 left handed helices combine in a triple right handed coil.
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lecture_17legge - Example of each level of protein...

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