BIO130H1 Lecture Notes - Lecture 3: Atp Hydrolysis, Symporter, Weak Interaction
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29 Mar 2017
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They are associated with the lipid bilayer in different ways. Integral membrane proteins: includes transmembrane proteins spans the whole lipid bilayer once or multiple times, integral membrane the protein penetrates or spans the lipid bilayer. Gpi-anchored proteins: anchored proteins can be anchored via a sugar or a lipid. Are amphipathic: hydrophilic domains aqueous. Aa side chains are polar: hydrophobic membrane-spanning domain. Transmembrane proteins: single-pass single alpha-helix, multi-pass multiple alpha-helices. Not all alpha helixes span the membrane. Receptors -> ion channels -> beta-barrel (a rolled beta-sheet) Beta-barrel some channels in bacteria, mitochondria, chloroplasts (rigid, don"t undergo conformational changes) Hydrophobicity plots: segments of 20-30 hydrophobic aa can span the lipid bilayer as an alpha helix. Proteins anchored on cytosolic face by an amphipathic alpha-helix b/c amino acids on one side face the tails, and amino acids on the other side face the water. Integral membrane protein does not have to span the entire membrane.