NiCoT family
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 . Reaction. The overall reaction catalyzed by the proteins of the NiCoT family is: 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.