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.
The three N-terminal domains form the "N-terminal cap." This structure caps a central domain containing three β-helices (one helix per subunit).
the central domains.
Now the assembly with the C-terminal domains.
One of the central domains is isolated, containing a large β-helix. Let's reassemble the β-helix sheet by sheet:
Next, the sheet.
Finally, the sheet.
Take a moment to sight down the axis of the β-helix before advancing.
Packing of the β helices into a three-helix bundle. spacefill.