pleated sheet One form of the secondary structure of proteins in which the polypeptide chain folds back and forth, or where two regions of the chain lie parallel to each other and are held together by hydrogen bonds. pleiotropy...  b-pleated sheet: A planar secondary structure element of proteins. The alpha helix and beta sheet are found at which level of protein? ... and the beta-pleated sheet (a little like the zigzag shape of a concertina). These shapes result from the intermolecular ... Dec 01, 1993 · In contrast, the beta-sheet content of PrPSc was 43% and the alpha-helix 30% as measured by FTIR. As determined in earlier studies, N-terminally truncated PrPSc derived by limited proteolysis, designated PrP 27-30, has an even higher beta-sheet content (54%) and a lower alpha-helix content (21%).