3.A.1.14.20
Heme-iron (hemin) utilization transporter BhuTUV ( Brickman et al., 2006; Vanderpool and Armstrong, 2004).  The crystal structures of BhuUV with or without the periplasmic haem-binding protein BhuT have been solved (Naoe et al. 2016). The TMSs show an inward-facing conformation, in which the cytoplasmic gate of the haem translocation pathway is completely open. Since this conformation is found in both the haem- and nucleotide-free form, the structure of BhuUV-T provides the post-translocation state and the missing piece in the transport cycle of type II importers.