Metal interactions with the transmembrane region of HupE Ni2Â + transporter explain its efficiency

The periplasmic region of the HupE nickel(II) transporter binds Ni2 + with much higher affinity than the transmembrane one, which should transport the metal inside the cell; this explains why HupE is a medium-affinity and low-capacity transporter. In both regions of the transporter, Cu2 + ions are able to outcompete Ni2 +.78