Which interaction commonly stabilizes a protein's tertiary structure by linking distant parts of the chain?

Which interaction commonly stabilizes a protein's tertiary structure by linking distant parts of the chain?

• A. Disulfide bonds
• B. Hydrogen bonds along the backbone
• C. Peptide bonds
• D. Ionic bonds between side chains

Answer: (A)

Cross-linking covalent bonds between distant parts of a protein is a powerful way to lock its three-dimensional shape in place. The disulfide bond forms when two cysteine amino acids come close enough for their sulfur atoms to bond, creating a covalent bridge that can connect far-apart regions of the same chain. This cross-linking greatly increases stability, especially for proteins exposed to harsh environments outside the cell. Other interactions contribute to structure but in different ways. Hydrogen bonds along the backbone mainly stabilize local secondary structures like helices and sheets, rather than tying distant parts of the chain together. Peptide bonds stitch the sequence together to form the primary structure, not the folded 3D shape. Ionic bonds between side chains can help stabilize some tertiary structure, but they are weaker and typically do not create the strong, covalent cross-links that hold distant regions in place.

Cross-linking covalent bonds between distant parts of a protein is a powerful way to lock its three-dimensional shape in place. The disulfide bond forms when two cysteine amino acids come close enough for their sulfur atoms to bond, creating a covalent bridge that can connect far-apart regions of the same chain. This cross-linking greatly increases stability, especially for proteins exposed to harsh environments outside the cell.

Other interactions contribute to structure but in different ways. Hydrogen bonds along the backbone mainly stabilize local secondary structures like helices and sheets, rather than tying distant parts of the chain together. Peptide bonds stitch the sequence together to form the primary structure, not the folded 3D shape. Ionic bonds between side chains can help stabilize some tertiary structure, but they are weaker and typically do not create the strong, covalent cross-links that hold distant regions in place.