Multiple choice

Which of the following amino acid change (mutation) would MOST adversely affect the structure of an $\alpha$-helix?

  1. A valine residue changed to an isoleucine residue

  2. A methionine residue changed to a proline residue

  3. An aspartic acid residue changed to a glutamic acid residue

  4. A histidine residue changed to an arganine residue
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Proline is an alpha-helix breaker because its rigid cyclic side chain lacks the hydrogen atom needed to participate in backbone hydrogen bonding and introduces a steric kink into the peptide chain.

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