TCDB is operated by the Saier Lab Bioinformatics Group

2.A.113 The Nickel/cobalt Transporter (NicO) Family

Homologues of the NicO family have differing predicted topologies: 6, 7 and 8 TMSs. One such homologue, RcnA (YohM) of E. coli (274 aas) has 6 putative TMSs in a 3+3 arrangement with a large hydrophilic loop between putative TMSs 3 and 4. This protein is believed to catalyze Co2+ and Ni2+ efflux (Marrero et al. 2007). Several homologues of RcnA (e.g., from Ralstonia solanacearum; 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 repeat unit of this family (within the LysE superfamily) may have a common orign with that in the NiCoT family (TC# 2.A.52) (within the TOG superfamily), having lost TMSs 1 and 4 in the 8 TMS TOG superfamily topology to give rise to a 3 TMS repeat unit. Thus, these two superfamilies may be related but different at the repeat unit level (M. Saier, unpublished observations).

The overall reaction catalyzed by proteins of the NicO family is probably:

[Ni2+ or Co2+] (in) [Ni2+ or Co2+] (out)

This family belongs to the: LysE Superfamily.

References associated with 2.A.113 family:

Marrero, J., G. Auling, O. Coto, and D.H. Nies. (2007). High-level resistance to cobalt and nickel but probably no transenvelope efflux: Metal resistance in the Cuban Serratia marcescens strain C-1. Microb Ecol 53: 123-133. 17186148
Protchenko, O., R. Rodriguez-Suarez, R. Androphy, H. Bussey, and C.C. Philpott. (2006). A screen for genes of heme uptake identifies the FLC family required for import of FAD into the endoplasmic reticulum. J. Biol. Chem. 281: 21445-21457. 16717099