Nickel transporters

Eitinger, T. Friedrich, B. Microbial Nickel Transport and Incorporation into Hy-drogenases Harwood Academic Publishers London, 1997. 

Figure 4.1 Nickel transport in . co//.The lower part of the figure shows the nik gene cluster from coli which encodes a nickel specific ABC-type transporter and the repressor protein (NikR).The likely roles of the various nik gene products are indicated in the upper part of the figure.The transporter is encoded by the nikBCDE genes whilst a periplasmic nickel-binding protein is encoded by n/M.The system is expressed when nickel is low. High nickel represses expression via NikR and under these conditions nickel is transported via the Mg transporter (top left).

Nickel availability to the host plants severely limits the expression of the R. leguminosarum hydrogenase genes in the P. sativum symbiosis (Brito et al. 1994) and probably in other symbioses such as M. loti-L. corniculatus (Brito et al. 2000). This limitation occurs at the level of processing of the enzyme subunits (Brito et al. 1994). It is not clear, however, whether Ni limitation is due to the bacterial or the plant component of the symbiosis. Recent results of nickel transport experiments with intact pea symbiosomes indicate that the peribacteroid membrane is not a specific barrier for Ni transport into the bacteroid (Bascones et al. unpublished). 

Eitinger, T. and Friedrich, B. (1991) Cloning, nucleotide sequence, and heterologous expression of a high-affinity nickel transport gene from Alcaligenes eutropbus. J. Biol. Cbem., 266, 3222-7. 

Eitinger, T. and Mandrand-Berthelot, M. A. (2000) Nickel transport systems in microorganisms. Arcb. Microbiol., 173, 1-9. 

Figure 6.1. Topological model for the HoxN nickel permease of R. eutropha that is like the HupN of B. japonicum (Eitinger et al. 1997). The residues (two histidines and one aspartic acid) in the second transmembrane segment were shown to be key residues for nickel transport, and this motif (His-Xaa4-Asp-His) is conserved in nickel-transport proteins. Bold, residues studied by site-directed mutagenesis.

Figure 6.4. Organization of the hydrogenase genes of B. japonicum. The nickel-transport related genes hupNOP located 5 of hupUV are not shown.

Eitinger T, Friedrich B. 1994. A topological model for the high-affinity nickel transport of Alcaligenes eutrophus. Mol Microbiol 12 1025-32. 

Mobley HLT, Garner RM, Bauerfeind R 1995. Helicobacter pylori nickel-transport gene AA synthesis of catalytically active urease in Escherichia coli independent of growth conditions. Mol Microbiol 16 97-109. 

Eitinger, T., and Eriedrich, B., 1997, Microbial nickel transport and incorporation into hydrogenases. Transition Metals in Microbial Metabolism. G. Winkelmann and C. Carrano. London, Harwood Academic Publishers 2350256. 

T. Eitinger and B. Friedrich, Microbial Nickel Transport and Incorporation into Hydrogenases, in Transition Metals in Microbial Metabolism , eds. G. Winkehnann and... 

Nickel Transport and Enzyme Active Site Assembly... 

---