Beta pleated sheet
Beta pleated sheet is an example of the secondary structure of a protein. The beta sheet is composed of beta strands which are polypeptides linked by hydrogen bonding. Beta strands have a 2 residues repeat and when the polypeptide is fully extended, the distance between adjacent amino acids is 3.5 A. The side chains of adjacent amino acids point in opposite directions which respect to each other. Valine, threonine, histidine, tyrosine and isoleucine are most likely to found in beta sheets. Whereas leucine, glutamate and alanine tend to be present in alpha helices.
Beta sheets come in two forms; anti-parallel and parallel. In anti-parallel the adjacent beta strands run in opposite directions, hydrogen bonding occurs between the NH group of one beta strand the C group of the adjacent strand. This forms regular straight bonds. The parallel beta sheet is the less stable arrangement and consists of both strands running in the same direction. The NH group hydrogen bonds to the CO group on the partner strand, but the CO group hydrogen bonds to the NH group on the adjacent strand two amino acids residues farther along the chain. .
Beta sheets can be parallel or antiparallel or be a mixture of the two.
- ↑ Berg J., Tymoczko J and Stryer L. (2007) Biochemistry, 6th edition, New York: WH Freeman