logo.gif (3296 bytes)Introduction to Protein Structure

Secondary Structure -- Beta Sheet


The backbone of an beta sheet (shown in color below) is arranged in zig-zag (or pleated fashion. Notice how the sidechains (shown in dark grey) stick from the backbone on each side of the sheet.The example show below is a three stranded beta sheet. A minimum of two strands is required to define a beta sheet; many beta sheets have more.

The beta sheet is stabilized by hydrogen bonds between the carbonyl oxygen of an amino acid in one strand and the backbone nitrogen of a second amino acid in another strand. Beta sheets can be either parallel or anti-parallel.  If the amino terminal residue of each strand "points" in the same direction the sheet is considered parallel. Anti-parallel sheets have the amino termini "pointing" in opposite directions.   Turn on the "highlight" in the figure below to color the amino terminal residue of each strand.

On

Off

H-bonds
Highlight
Sidechains

This beta sheet consists of residues 42-46, 49-54 and 56-60 in chicken egg white lysozyme.


Copyright 1998, 1999, 2007 by Frank R. Gorga;   Page maintained by F.R. Gorga;   Last updated: 12-Mar-2007