Figure 4: ZnuD is not a haem translocator.
From: The molecular mechanism of Zinc acquisition by the neisserial outer-membrane transporter ZnuD
Cartoon representation of the TonB-dependent receptors HasR (a) (pdb code 3CSL)2 and ZnuD (b); the boxes highlight an enlarged view of their high-affinity binding sites for haem and zinc, respectively. HasR and ZnuD share a common mechanism to clamp their cognate substrates using two facing histidines from extracellular loop 6 and the plug-apical loop. (c) Coomassie-stained SDS–PAGE illustrating the haem-binding profile of ZnuD and haemoglobin using haem-agarose beads. Lane 1 is the molecular weight marker; lanes 2 and 3 are the supernatant and the haem-bead pelleted fractions for the haemoglobin-binding assay (positive control); lanes 4 and 5 are the supernatant and the haem-bead pelleted fractions for the ZnuD-binding experiments.
