NiCoT family
Proteins currently known to belong to the Ni2+-Co2+ 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 Ni2+ and/or Co2+ in a proton motive force-dependent process.[1]
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 Ni2+ transporter of Ralstonia eutropha (Alcaligenes eutrophus) suggest that it possesses 8 TMSs with its N- and C-termini in the cytoplasm. The Co2+ (Ni2+) 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 HX4DH motif in helix 2 of the HoxN protein has been implicated in Ni2+ binding, and both helix 1 and helix 2, which interact spatially, form the selectivity filter.[2] In the Helicobacter pylori NixA homologue, several conserved motifs have been shown to be important for Ni2+ binding and transport.[1][3]
At least one crystal structure is known, determined by Yu et al.,[4] available at PDB: 4M58.
Reaction
The overall reaction catalyzed by the proteins of the NiCoT family is:[1]
- [Ni2+ and/or Co2+] (out) → [Ni2+ and/or Co2+] (in).
Proteins
Several characterized proteins belong to the Ni2+-Co2+ 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
- ^ a b c 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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