Beta sheet

A protein secondary structure made of extended polypeptide strands aligned side by side and stabilized by hydrogen bonds between their backbones. Its strands can run in parallel or antiparallel directions.

Beta strand: An extended segment of a polypeptide chain that can hydrogen-bond with neighboring strands in a beta sheet. Each sheet is assembled from these extended backbone segments.
Protein backbone: The repeating chain of atoms linking amino-acid residues in a protein. Its carbonyl and amide groups form the sheet’s hydrogen bonds.
Immunoglobulin fold: A protein domain fold built around two opposing beta sheets packed together. It shows how sheets create a stable scaffold for antibody domains.
Alpha helix: A protein secondary structure in which a polypeptide backbone coils into a hydrogen-bonded helix. Unlike a sheet, its backbone hydrogen bonds form within one helical segment.
Backbone hydrogen bond: An interaction between a backbone carbonyl oxygen and an amide hydrogen in a protein or peptide. These bonds connect neighboring strands and stabilize the sheet.
Peptide bond: The covalent bond joining amino acids in a polypeptide chain. Peptide-bond planarity constrains the backbone that forms each strand.
Beta-propeller: A protein fold of radially arranged beta-sheet blades forming a propeller-like structure. Repeated sheet units assemble into a distinctive architecture for binding and catalysis.
Polyproline helix: An extended protein conformation common in proline-rich sequences, with a helical rather than sheet arrangement. It is extended like a strand but lacks the usual beta-sheet hydrogen-bond network.
Parallel beta sheet: A beta sheet whose neighboring strands run in the same N-to-C direction. This arrangement changes the geometry of inter-strand hydrogen bonds.
Amino acid: An organic molecule that serves as a building block of proteins. Residue properties influence which sheet arrangements a sequence can adopt.

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