2011_09_26_fibrous_proteins_membrane_proteins_symmetry

2011_09_26_fibrous_proteins_membrane_proteins_symmetry -...

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Unformatted text preview: Fibrous Proteins • Main role is structural • Form long cable-like molecules • Examples from both alpha (collagen) and beta (silk fibroin) folds exist • Usually have specific patterns of residues that repeat as we saw for the coiled coils (heptad repeat) • Generally divided into 3 categories:1) coiled-coils (keratin), 2) triple helix (collagen), 3) !-sheets (silks) Coiled-coil fibrous proteins • Include myosin, fibrinogen, spectrin, keratin (intermediate filaments) • Keratins are structural proteins of skin, hair, wool, horn, feathers • Exhibit heptad repeats in the central helical regions (~300 residues) • Relatively high disulfide content gives hair its elasticity (human hair ~14% cysteine - curly hair has higher disulfide bond content) • Activity of a hair follicle = 6 inches/year = 9.5 turns of a helix/ Coiled-coil fibrous proteins • Include myosin, fibrinogen, spectrin, keratin (intermediate filaments) • Keratins are structural proteins of skin, hair, wool, horn, feathers • Exhibit heptad repeats in the central helical regions (~300 residues) • Relatively high disulfide content gives hair its elasticity (human hair ~14% cysteine - curly hair has higher disulfide bond content) • Activity of a hair follicle = 6 inches/year = 9.5 turns of a helix/ sec, this diet of amino acids can affect composition of hair monomer parallel dimer antiparallel tetramer Anatomy of a Hair Strand macrofibril microfibril Collagen forms a triple helix - Collagen is a trimer with repeat sequence: Gly-X-Y, where X is usually Pro and Y is usually hydroxyPro - HydroxyPro formed by post- translational modification of Pro - Each chain forms a less compact left-handed helix (3.3 residues/turn, 9.6 Å rise/turn) called the poly-Pro Type II helix - 3 left-handed helices trimerize to form a right-handed superhelix - Collagen forms supramolecular structures in the extracellular space...
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This note was uploaded on 10/21/2011 for the course BIOC 450 and 45 taught by Professor Various during the Fall '11 term at McGill.

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2011_09_26_fibrous_proteins_membrane_proteins_symmetry -...

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