Figure 3.

Extracellular loop stability in crystal states of Fiu and PiuA/PiuD. A, stereo cartoon view of Fiu in crystal states 1 and 2, illustrating the variably ordered extracellular barrel loops 7, 8, and 9 (L7–L9) and the plug domain loop (PL). Loops are color-coded as follows: L7, salmon; L8, red; L9, brick red; plug domain loop, blue. Loop termini are shown as spheres where the loop is disordered. B, PiuA and PiuD crystal structures from P. aeruginosa and A. baumannii presented as for Fiu in A. The crystal structures of PiuA and PiuD display an analogous pattern of loop order/disorder to that observed for Fiu. C, cutaway outline representation of PiuA and PiuD, showing the presence of a selectively gated internal cavity. Outer membrane is abbreviated to OM in this figure.