InterPro domain: IPR011042

This superfamily represents a six-bladed beta-propeller domain consisting of six 4-stranded beta-sheet motifs. This domain can be found in TolB proteins (C-terminal), in soluble quinoprotein glucose dehydrogenase, in calcium-dependent phosphotriesterases, in the low density lipoprotein (LDL) receptor YWTD domain, in nidogen, and in serine/threonine-protein kinase (PknD) NHL repeat domain.

TolB is a periplasmic protein from Escherichia coli that is part of the Tol-dependent translocation system involving group A and E colicins that is used to penetrate and kill cells [ 1 , 2 ]. TolB has two domains, an alpha-helical N-terminal domain that shares structural similarity with the C-terminal domain of transfer RNA ligases, and a beta-propeller C-terminal domain that shares structural similarity with numerous members of the prolyl oligopeptidase family and, to a lesser extent, to class B metallo-beta-lactamases (although its does not necessarily occur at the C-terminal in these proteins) [ 3 ]. The C-terminal domain of TolB may mediate protein-protein interactions with colicins.

1. Structure of the Escherichia coli TolB protein determined by MAD methods at 1.95 A resolution. Structure 7, 1291-300
2. The structure of TolB, an essential component of the tol-dependent translocation system, and its protein-protein interaction with the translocation domain of colicin E9. Structure 8, 57-66