A structural feature shared by all alpha-helices and all beta-sheets in proteins is
A) covalent modification by phosphorylation.
B) cross links through disulfide bonds.
C) minimal exposure on the surface.
D) proteolytic digestion by trypsin.
E) stabilization by hydrogen bonds.

Question

Quizplus · Accepted Answer

Both alpha-helices and beta-sheets are stabilized by hydrogen bonds. In alpha-helices, the hydrogen bonds form between the carbonyl group of the amino acid residue i and the amide group of residue i+4. In beta-sheets, the hydrogen bonds form between adjacent strands in the sheet. Covalent modification, disulfide bonds, minimal exposure on the surface, and proteolytic digestion are not structural features shared by all alpha-helices and beta-sheets.

A Structural Feature Shared by All Alpha-Helices and All Beta-Sheets