Multiple Choice
Which of the following options contains a true statement about protein turns & loops?
4. Protein Structure
Beta Turns
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Which of the following statements is correct?
A
Loops and turns are usually found tucked away on the interior of folded proteins.
B
An α-helix peptide backbone located in the interior of a protein will H-bond to R-groups of other residues.
C
In extended fibrous proteins that are elongated, we would expect to find numerous β-turns & loops.
D
Tightly compact spherical/globular proteins tend to have more β-turns than elongated fibrous proteins.
E
A membrane-embedded α-helix is likely rich in Asp residues.
Verified step by step guidance1
Understand the structure of proteins: Proteins can be classified into two main types based on their shape: globular and fibrous. Globular proteins are compact and spherical, while fibrous proteins are elongated and strand-like.
Examine the role of β-turns: β-turns are short sequences of amino acids that connect the ends of two adjacent segments of an antiparallel β-sheet. They are more common in globular proteins due to their compact nature, which requires tight turns to fold into a spherical shape.
Consider the location of loops and turns: Loops and turns are typically found on the surface of proteins, not tucked away in the interior. They often participate in interactions with other molecules or proteins.
Analyze the hydrogen bonding in α-helices: In an α-helix, the peptide backbone forms hydrogen bonds with itself, not with the R-groups of other residues. This stabilizes the helical structure.
Evaluate the composition of membrane-embedded α-helices: Membrane-embedded α-helices are usually rich in hydrophobic residues, such as leucine, isoleucine, and valine, to interact favorably with the lipid bilayer. Aspartic acid (Asp) is a charged, hydrophilic residue and is less likely to be found in membrane-spanning regions.
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