BCH210H1 Chapter Notes - Chapter 30: Beta Sheet, Cell Membrane
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BCH210H1 Full Course Notes
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3. 6 residues per turn = 5. 4a = . 54nm. Distance between each residue = 1. 5a = 0. 15nm. Membrane protein folding: hydrophobic stretches of amino acids cross membranes as alpha helices to neutralize the polar backbone, problem #2, hydrophobic amino acids generally have low propensity to form alpha helices (according to chou-fasman parameters) Val, ile, phe are top beta sheet formers. Itliifgvmagvigtilli: rich in beta sheet residues and contains 3 gly"s which are the best alpha helices breakers. Backbone neutralization and hydrophobicity supersede amino acid structural propensities: the mid-range amino acid gly is often involved in helix-helix interactions, small side chain allows two helices to get close together. Glycophorin a self-associates via transmembrane helices: gly"s allow the close approach of transmembrane helices, allows for extensive van der waals contact. Multi-spanning membrane proteins: most helical membrane proteins cross the lipid bilayer more than once. Membrane protein structure: historically very difficult to characterize.
