Final answer:
Type 1 and type 2 beta turns are two common types of beta turns in proteins. Type 1 beta turns have a 180-degree change in direction and are stabilized by a hydrogen bond between residues i and i+3. Type 2 beta turns have a 360-degree change in direction and are stabilized by a hydrogen bond between residues i-1 and i+2.
Step-by-step explanation:
There are several types of beta turns in proteins, but the most common are type 1 and type 2 beta turns. Type 1 beta turns are characterized by a hydrogen bond between the carbonyl oxygen of residue i and the amide nitrogen of residue i+3. This creates a tight turn with a 180-degree change in direction of the protein backbone. Type 2 beta turns, on the other hand, do not have a hydrogen bond between residues i and i+3, but instead have a hydrogen bond between the carbonyl oxygen of residue i-1 and the amide nitrogen of residue i+2. This results in a more extended turn with a 360-degree change in direction. Both types of beta turns play important roles in protein structure and function.