One of the most common 2 o folding patterns is called the alpha-helix , discovered by Pauling and Corey. This regular pairing pulls the polypeptide into a helical shape that resembles a coiled ribbon. Another common folding pattern is called beta pleated sheet . Some protein regions remain in random coil, no regular pattern of secondary structure. Different proteins have different degrees of alpha helix, beta sheet, and random coil .
Most proteins have some of both.
Review 2 o structure at The Biology Place. 3 o Structure Polypeptides continue folding beyond the formation of secondary structure. These are especially important, because they are covalent bonds and quite strong compared to H-bonds. Some proteins are made of multiple polypeptide subunits, which must be assembled together after each individual polypeptide has reached its 3 o structure. If Chime plug-in is installed, View Tutorial on Insulin Structure for review.