Beta-pleated sheet

The three-dimensional structures of transthyretin and immunoglobulin κ light chain are shown on the left. Ribbons correspond to portions of the molecules found to have a beta-pleated sheet configuration by X-ray crystallography; molecular domains adopting a predominantly alpha helical configuration are shown as coils, the remainder being peptide sequences that have a random configuration. As shown on the right, both polypeptide chains converge into a cross-beta super-secondary structure that has been well characterized by X-ray diffraction, with prototypical interstrand and intersheet distances of 4.7 and 10 to 13 Å, respectively.