"The beta sheet is another common secondary structure. In contrast to an alpha helix, it is formed by hydrogen bonds between backbone atoms on adjacent regions of the peptide backbone, called beta strands. These interactions do not involve side chains. Thus, many different sequences can form a beta sheet. A beta sheet is a regular and rigid structure often represented as a series of flattened arrows. Each arrow points towards the proteins C-terminus. In the example shown here the two middle strands run parallel—that is, in the same direction—whereas the peripheral strands are antiparallel. The amino acid side chains from each strand alternately extend above and below the sheet, thereby allowing each side to have distinct properties from the other. Beta sheets are usually twisted and not completely flat."
Essential Cell Biology, Second Edition
by Alberts, Bray, Hopkin, Johnson, Lewis, Raff, Roberts, Walter
copyright 2004 by Garland Science Publishing
