6-bladed beta-propeller protein: Neuraminidase

Cartoons view of neuraminidase, a 6-bladed beta-propeller. Notice that one strand at the N-terminus, colored blue, forms an antiparallel beta-sheet with 3 strands from the C-terminus, colored red.

The active site of such a protein is typically formed by the loops that will eventually face you.

A single blade of the propeller, consists of 4 anti-parallel beta-strands. This one has a very short helix in the center loop.

1a4q (PDB)

Taylor, N. R., Cleasby, A., Singh, O., Skarzynski, T., Wonacott, A. J., Smith, P. W., Sollis, S. L., Howes, P. D., Cherry, P. C., Bethell, R., Colman, P., Varghese, J.: Dihydropyrancarboxamides related to zanamivir: a new series of inhibitors of influenza virus sialidases. 2. Crystallographic and molecular modeling study of complexes of 4-amino-4H-pyran-6-carboxamides and sialidase from influenza virus types A and B. J Med Chem 41 pp. 798 (1998) (PubMed)

Varghese JN, Laver WG, Colman PM.
Structure of the influenza virus glycoprotein antigen neuraminidase at 2.9 A resolution.
Nature. 1983 May 5-11;303(5912):35-40 (PubMed)