Figure 2.

The crystal structure of Fiu reveals a large gated internal cavity. A, the crystal structure of fully ordered Fiu (crystal state 2), shown as a cartoon representation with rainbow colors running from N-terminal (blue) to C-terminal (red). B, cutaway outline representation of Fiu crystal structures, showing the internal cavity selectively occluded in crystal state 2 as well as the effect of removal of the labile subdomain of the TBDT plug on Fiu channel formation through the membrane. C, composite cutaway view of Fiu, showing the N-terminal plug domain as a cartoon, with the variably ordered plug loop (blue) and labile plug subdomain (red) highlighted. Outer membrane is abbreviated to OM in this figure.