Opening image: The tailspike protein of Salmonella phage P22. The 150-Å-long molecule is a part of the apparatus by which the phage attaches to the bacterial host. Each subunit of the homo-trimer contains a large β helix.
Each subunit consists of 666 amino-acid residues which can be divided into three domains.
one of the three subunits. Then, the domains; the N-terminal domain is shown in blue, the central domain in purple, and the C-terminal domain in red.