What holds a beta-pleated sheet together?
Hydrogen bonds again. Strands of peptide chains lay next to each other in a “sheet” pattern. They can be facing in opposite directions (anti-parellel, most stable, most common), or facing in the same direction (parellel, less stable). Amyloid protein of Alzheimer’s disease is mainly beta sheet. Beta bends connect adjacent beta strands. 10. What is a protein domain? A: A domain refers to a specific region of a protein. A structural domain could be a region of alpha-helices grouped together. A functional domain could be the binding region for a receptor or the catalytic site of an enzyme. A single protein can have multiple domains. Think of a 2nd-messenger-linked receptor with a receptor domain and an intracellular activation domain. 11. What holds a protein’s tertiary structure together? What keeps it wrapped up properly? A: Covalent bonds: disulfide bonds between cysteine residues. Hydrophobic forces: the interior of the protein tries to stay away from water by surrounding itself with
