Beta sheet
![An example of a 4-stranded antiparallel β-sheet fragment from a crystal structure of the enzyme catalase (PDB file 1GWE at 0.88Å resolution). a) Front view, showing the antiparallel hydrogen bonds (dotted) between peptide NH and CO groups on adjacent strands. Arrows indicate chain direction, and electron density contours outline the non-H atoms. O atoms are red balls, N atoms are blue, and H atoms are omitted for simplicity; sidechains are shown only out to the first sidechain C atom (green). b) Edge-on view of the central two β-strands in a, showing the righthanded twist and the pleat of Cαs and sidechains that alternately stick out in opposite directions from the sheet.](/Images/godic/202502/03/1gwe_antipar_betaSheet_both0312.png")
![Antiparallel β-sheet hydrogen bonding patterns, represented by dotted lines. Oxygen atoms are colored red and nitrogen atoms colored blue.Parallel β-sheet hydrogen bonding patterns, represented by dotted lines. Oxygen atoms are colored red and nitrogen atoms colored blue.](/Images/godic/202502/03/Beta_sheet_bonding_antiparallel-color.svg0312.png")
![](/Images/godic/202502/03/Beta_sheet_bonding_parallel-color.svg0312.png")
![Ramachandran (φ,ψ) plot of about 100,000 high-resolution datapoints, showing the broad, favorable region around the conformation typical for β-sheet residues.](/Images/godic/202502/03/Ramachandran_plot_general_100K0312.jpg")
The β-sheet (also β-pleated sheet) is the second form of regular secondary structure in proteins. Beta sheets consist of beta strands (also β-strand) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation. The higher-level association of β-sheets has been implicated in formation of the protein aggregates and fibrils observed in many human diseases, notably the amyloidoses such as Alzheimer's disease.