NicO transporters

The Nickel/Cobalt Transporter (NicO) Family (TC# 2.A.113) is a member of the Lysine Exporter (LysE) Superfamily. A representative list of proteins belonging to the NicO family can be found in the Transporter Classification Database.
Homology.
Homologues of the NicO family have differing predicted topologies: 6, 7 and 8 TMSs. One such homologue, RcnA (YohM; TC# 2.A.113.1.1) of "E. coli" (274 aas) has 6 putative transmembrane segments (TMSs) in a 3 + 3 arrangement with a large hydrophilic loop between putativeTMSs 3 and 4. Several homologues of RcnA (e.g., RcnA homologue from "Ralstonia solanacearum"; TC# 2.A.113.1.3; CAD17703) have 7 putative TMSs (4 + 3). Still another homologue, UreH of "Methanocaldococcus janaschii" (TC# 2.A.113.1.4) has 6 putative TMSs in a more characteristic 3 + 3 TMS arrangement. The NicO family within the LysE superfamily may have a common origin with the TOG superfamily, having lost TMSs 1 and 4 in the 8 TMS TOG superfamily topology.
Function.
This protein is believed to catalyze Co2+ and Ni2+ efflux.
The overall reaction catalyzed by proteins of the NicO family is probably:
[Ni2+ or Co2+] (in) → [Ni2+ or Co2+] (out).