Proteins currently known to belong to the Ni-Co Transporter (NiCoT) family (TC# 2.A.52) can be found in organisms ranging from Gram-negative and Gram-positive bacteria to archaea and some eukaryotes. Members of this family catalyze uptake of Ni and/or Co in a proton motive force-dependent process.
Structure
These proteins range in size from about 300 to 400 amino acyl residues and possess 6, 7, or 8 transmembrane segments (TMSs), thought to result from an intragenic 4 TMS duplication, followed by a deletion of one or two TMSs in the cases of the 7 or 6 TMS proteins. Topological analyses with the HoxN Ni transporter of Ralstonia eutropha (Alcaligenes eutrophus) suggest that it possesses 8 TMSs with its N- and C-termini in the cytoplasm. The Co (Ni) transporter of Rhodococcus rhodochrous, NhlF, exhibits eight putative TMSs, and eight apparent TMSs are revealed by hydropathy analyses of multiple alignments of family protein sequences. An HXDH motif in helix 2 of the HoxN protein has been implicated in Ni binding, and both helix 1 and helix 2, which interact spatially, form the selectivity filter. In the Helicobacter pylori NixA homologue, several conserved motifs have been shown to be important for Ni binding and transport.
At least one crystal structure is known, determined by Yu et al., available at PDB: 4M58.
Reaction
The overall reaction catalyzed by the proteins of the NiCoT family is:
- (out) → (in).
Proteins
Several characterized proteins belong to the Ni-Co Transporter (NiCoT) Family (TC# 2.A.43). A complete list of these proteins along with their transporter classification identification numbers (TCID), domain, kingdom/phylum, and some examples can be found in the Transporter Classification Database.
References
- ^ Saier, Milton. "Transporter Classification Database: 2.A.52 The Ni2+-Co2+ Transporter (NiCoT) Family". tcdb.org. Retrieved 4 January 2016.
- Degen, O; Eitinger, T (July 2002). "Substrate specificity of nickel/cobalt permeases: insights from mutants altered in transmembrane domains I and II". J. Bacteriol. 184 (13): 3569–77. doi:10.1128/jb.184.13.3569-3577.2002. PMC 135128. PMID 12057951.
- Wolfram, L; Bauerfeind, P (March 2002). "Conserved low-affinity nickel-binding amino acids are essential for the function of the nickel permease NixA of Helicobacter pylori". J. Bacteriol. 184 (5): 1438–43. doi:10.1128/JB.184.5.1438-1443.2002. PMC 134868. PMID 11844775.
- Yu, Y; Zhou, M; Kirsch, F; Xu, C; Zhang, L; Wang, Y; Jiang, Z; Wang, N; Li, J; Eitinger, T; Yang, M (December 24, 2013). "Planar substrate-binding site dictates the specificity of ECF-type nickel/cobalt transporters". Cell Research. 24 (3): 267–277. doi:10.1038/cr.2013.172. PMC 3945884. PMID 24366337.
Further reading
- Deng, X; He, J; He, N (February 2013). "Comparative study on Ni(2+)-affinity transport of nickel/cobalt permeases (NiCoTs) and the potential of recombinant Escherichia coli for Ni(2+) bioaccumulation". Bioresour. Technol. 130: 69–74. doi:10.1016/j.biortech.2012.11.133. PMID 23306112.
- Rodionov, D; Hebbeln, P; Gelfand, M; Eitinger, T (January 2006). "Comparative and Functional Genomic Analysis of Prokaryotic Nickel and Cobalt Uptake Transporters: Evidence for a Novel Group of ATP-Binding Cassette Transporters". J. Bacteriol. 188 (1): 317–327. doi:10.1128/JB.188.1.317-327.2006. PMC 1317602. PMID 16352848.
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