Lehninger 8e: Lipid Annuli in Membrane Proteins
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Questions and Answers

What is the role of annular lipids in membrane proteins?

  • Encapsulate the protein in a water layer
  • Enhance protein flexibility in the membrane
  • Repel proteins from the membrane surface
  • Form a bilayer shell around the protein (correct)
  • Which amino acid residues are commonly found at the interface between lipid and water in transmembrane proteins?

  • Cysteine and Serine
  • Alanine and Glycine
  • Tyrosine (Tyr) and Tryptophan (Trp) (correct)
  • Phenylalanine (Phe) and Methionine (Met)
  • How do proteins with a narrow hydrophobic band influence lipids in the membrane?

  • Promote lipid bilayer formation around the protein
  • Enhance lipid-protein interactions
  • Encourage lipids to take on less extended conformations (correct)
  • Repel lipids from the protein surface
  • What is the main function of charged residues like Arginine (Arg) and Lysine (Lys) in membrane proteins?

    <p>Act as anchors in the aqueous phase</p> Signup and view all the answers

    Which of the following characteristics apply to α-helical proteins in membrane-spanning segments?

    <p>About 18-20 residues needed to span the membrane</p> Signup and view all the answers

    What type of irregularities are commonly observed in helices of multi-spanning membrane proteins?

    <p>Over-wound regions, kinks, local unfolding</p> Signup and view all the answers

    What kind of residues are favored in the interfacial region of the membrane-spanning helix?

    <p>Aromatic residues</p> Signup and view all the answers

    Why is tilting the helix problematic in spanning a biological membrane?

    <p>It may not effectively span the membrane due to a limited number of residues</p> Signup and view all the answers

    What role does the C-terminal end of the helix play in a bacterial K+ channel?

    <p>Stabilizes K+ ions and acts as a specificity filter</p> Signup and view all the answers

    Which type of proteins are especially abundant and have 4, 7, or 12 transmembrane segments?

    <p>G-protein coupled receptors (GPCRs)</p> Signup and view all the answers

    What kind of residues predominantly make up the central region of multi-spanning trans-membrane proteins?

    <p>Hydrophilic residues</p> Signup and view all the answers

    Which residue type is tolerated in small numbers in the section of the helix traversing the membrane?

    <p>Weakly hydrophilic residues (e.g., Thr, Ser)</p> Signup and view all the answers

    What is the most abundant group of residues in transmembrane helices?

    <p>Small to midsized hydrophobic residues</p> Signup and view all the answers

    Which type of residues are rare in transmembrane helices?

    <p>Charged residues</p> Signup and view all the answers

    What kind of amino acids are often present in transmembrane domains involved in transport, ligand binding, and catalysis?

    <p>Polar amino acids</p> Signup and view all the answers

    How do hydrophilic side chains in transmembrane domains interact with the lipid bilayer?

    <p>They face the interior of the bundle</p> Signup and view all the answers

    In the structure of the glucose transporter, what lines the hydrophilic transmembrane pore?

    <p>Polar amino acids</p> Signup and view all the answers

    What stabilizes the structure of membrane proteins by interacting with the lipid bilayer?

    <p>Small to midsized hydrophobic residues</p> Signup and view all the answers

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