Final answer:
The β-pleated sheet in proteins is characterized by two or more polypeptide chains aligned parallel or antiparallel, stabilized by hydrogen bonds between peptide bond elements, and contributes to fibrous protein structures and enzyme regions.
Step-by-step explanation:
The β-pleated sheet is a secondary structure found in proteins that is characterized by its sheet-like arrangement of backbone chains in polypeptides. In a β-pleated sheet, two or more extended polypeptide chains are aligned either parallel or antiparallel to each other, and the arrangement can include diverse combinations of these orientations. The hydrogen bonds form between the partially positive nitrogen atom in the amino group and the partially negative oxygen atom in the carbonyl group of the peptide bonds. The phi (φ) and psi (ψ) angles in the sheet configurations influence the folding and pleating of the polypeptide chains. The β-pleated sheet is a crucial structural component in fibrous proteins like silk fibroin and in various enzymes.