18 Questions
What is the role of annular lipids in membrane proteins?
Form a bilayer shell around the protein
Which amino acid residues are commonly found at the interface between lipid and water in transmembrane proteins?
Tyrosine (Tyr) and Tryptophan (Trp)
How do proteins with a narrow hydrophobic band influence lipids in the membrane?
Encourage lipids to take on less extended conformations
What is the main function of charged residues like Arginine (Arg) and Lysine (Lys) in membrane proteins?
Act as anchors in the aqueous phase
Which of the following characteristics apply to α-helical proteins in membrane-spanning segments?
About 18-20 residues needed to span the membrane
What type of irregularities are commonly observed in helices of multi-spanning membrane proteins?
Over-wound regions, kinks, local unfolding
What kind of residues are favored in the interfacial region of the membrane-spanning helix?
Aromatic residues
Why is tilting the helix problematic in spanning a biological membrane?
It may not effectively span the membrane due to a limited number of residues
What role does the C-terminal end of the helix play in a bacterial K+ channel?
Stabilizes K+ ions and acts as a specificity filter
Which type of proteins are especially abundant and have 4, 7, or 12 transmembrane segments?
G-protein coupled receptors (GPCRs)
What kind of residues predominantly make up the central region of multi-spanning trans-membrane proteins?
Hydrophilic residues
Which residue type is tolerated in small numbers in the section of the helix traversing the membrane?
Weakly hydrophilic residues (e.g., Thr, Ser)
What is the most abundant group of residues in transmembrane helices?
Small to midsized hydrophobic residues
Which type of residues are rare in transmembrane helices?
Charged residues
What kind of amino acids are often present in transmembrane domains involved in transport, ligand binding, and catalysis?
Polar amino acids
How do hydrophilic side chains in transmembrane domains interact with the lipid bilayer?
They face the interior of the bundle
In the structure of the glucose transporter, what lines the hydrophilic transmembrane pore?
Polar amino acids
What stabilizes the structure of membrane proteins by interacting with the lipid bilayer?
Small to midsized hydrophobic residues
Explore the concept of lipid annuli (boundary lipids) in membrane proteins as discussed in Figure 11.32 on page 388 of Lehninger 8th edition. Learn about the arrangement, interactions, and significance of annular lipids surrounding membrane proteins.
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