Page 173 - The Manga Guide to Biochemistry

Secondary Structure of a Protein

Each of the 20 amino acids has a characteristic part (indicated by [R] on page 155) that is
unique. This is called the side chain.

Since a number of difference forces can act on these side chains, such as hydrogen
bonds and hydrophobic and electrostatic interactions, neighboring amino acids are attracted
to or repelled by each other in particular ways, which results in a characteristic, local three-
dimensional structure. This is called the secondary structure of the protein.

There are a number of different secondary structures, such as an α-helix, in which
a part of the polypeptide chain forms a spiral, and a β-sheet, which takes a folded planar
shape.

α-helix β-sheet

Primary structure secondary structure

Enzymes Are the Keys to Chemical Reactions 159