β-sheets

Definition

β-sheets are a secondary structure of proteins where multiple polypeptide chains or strands are arranged in a flat, pleated configuration held together by hydrogen bonds. They are one of the fundamental structural elements that contribute to the overall three-dimensional folding of proteins.

5 Must Know Facts For Your Next Test

1. β-sheets are formed when two or more polypeptide chains or strands align parallel or antiparallel to each other and are stabilized by hydrogen bonds between the carbonyl oxygen and amino hydrogen atoms of adjacent strands.
2. The pleated appearance of β-sheets arises from the alternating pattern of the carbonyl and amino groups in the polypeptide backbone.
3. β-sheets can be classified as either parallel or antiparallel, depending on the orientation of the adjacent polypeptide strands.
4. The formation of β-sheets is driven by the need to maximize hydrogen bonding and minimize the exposure of hydrophobic amino acid side chains to the aqueous environment.
5. β-sheets are commonly found in proteins that require structural rigidity and stability, such as enzymes, antibodies, and structural proteins.

Review Questions

• Describe the structural features and arrangement of amino acid residues in a β-sheet.
  • In a β-sheet, multiple polypeptide chains or strands are arranged in a flat, pleated configuration and held together by hydrogen bonds between the carbonyl oxygen and amino hydrogen atoms of adjacent strands. The pleated appearance is due to the alternating pattern of the carbonyl and amino groups in the polypeptide backbone. The strands can be oriented either parallel or antiparallel to each other, and the formation of β-sheets is driven by the need to maximize hydrogen bonding and minimize the exposure of hydrophobic amino acid side chains to the aqueous environment.
• Explain the role of β-sheets in the overall folding and stability of protein structures.
  • β-sheets are one of the fundamental secondary structures that contribute to the overall three-dimensional folding of proteins. The hydrogen bonding between adjacent polypeptide strands in a β-sheet provides significant structural rigidity and stability to the protein. This allows proteins to adopt complex tertiary and quaternary structures that are necessary for their biological functions, such as enzymatic catalysis, antibody recognition, and the formation of structural proteins. The ability of β-sheets to maximize hydrogen bonding and minimize the exposure of hydrophobic regions is a key factor in the efficient and stable folding of proteins.
• Analyze the potential impact of mutations or disruptions to β-sheet formation on protein structure and function.
  • Mutations or disruptions to the formation of β-sheets can have significant consequences on the overall structure and function of proteins. Changes to the amino acid sequence that disrupt the hydrogen bonding patterns or the alignment of polypeptide strands in a β-sheet can lead to misfolding or the adoption of an incorrect tertiary structure. This can result in the loss of a protein's biological activity, such as the inability to catalyze a specific reaction or to properly bind to its target. Disruptions to β-sheet formation can also compromise the structural integrity of proteins, making them more susceptible to denaturation or aggregation, which can further impair their function. Understanding the critical role of β-sheets in protein folding and stability is essential for predicting the effects of genetic mutations and designing effective therapeutic interventions for protein-related diseases.

Related terms

Polypeptide Chain: A long, linear sequence of amino acids that forms the basic structural unit of a protein.

Hydrogen Bonding: A type of dipole-dipole attraction that occurs between a hydrogen atom attached to a highly electronegative atom and another highly electronegative atom.

Protein Folding: The process by which a protein structure assumes its functional 3D shape from a random coil state.