Beta-sheet

A beta-sheet (also β-sheet) is a common motif of the regular secondary structure in proteins. Beta-sheets consist of beta-strands (also β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A beta-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with its backbone in an extended conformation.

Structure

Beta-sheets are formed by linking two or more beta-strands by hydrogen bonds. The beta-strands are aligned adjacent to each other, forming a sheet-like structure. The hydrogen bonds are formed between the carbonyl oxygen of one amino acid and the amide hydrogen of another. Beta-sheets can be either parallel or antiparallel, depending on the relative orientation of the beta-strands.

Parallel Beta-Sheets

In parallel beta-sheets, the beta-strands run in the same direction (N-terminus to C-terminus). The hydrogen bonds in parallel beta-sheets are slightly distorted compared to those in antiparallel beta-sheets, making them less stable.

Antiparallel Beta-Sheets

In antiparallel beta-sheets, the beta-strands run in opposite directions. The hydrogen bonds in antiparallel beta-sheets are more linear and thus stronger, making these sheets more stable than parallel beta-sheets.

Function

Beta-sheets play a crucial role in the structural integrity of many proteins. They are found in a variety of proteins, including enzymes, antibodies, and structural proteins. Beta-sheets contribute to the overall stability and rigidity of the protein structure.

Examples

Beta-sheets are present in many well-known proteins. For example, they are a key structural component of fibroin, the protein in silk. They are also found in the immunoglobulin fold, which is a common feature of antibodies.

Related Pages

• Alpha helix
• Protein structure
• Hydrogen bond
• Amino acid
• Polypeptide
• Enzyme
• Antibody
• Fibroin
• Immunoglobulin