RcnB is a family of Proteobacteria proteins. RcnB is required for maintaining metal ion homeostasis, in conjunction with the efflux pump RcnA, family NicO, Pfam:PF03824 [1].

1: Identification of rcnA (yohM), a nickel and cobalt resistance gene in Escherichia coli. Rodrigue A, Effantin G, Mandrand-Berthelot MA; J Bacteriol. 2005;187:2912-2916. PMID:15805538

2: Nickel homeostasis in Escherichia coli - the rcnR-rcnA efflux pathway and its linkage to NikR function. Iwig JS, Rowe JL, Chivers PT; Mol Microbiol. 2006;62:252-262. PMID:16956381

3: RcnB is a periplasmic protein essential for maintaining intracellular Ni and Co concentrations in Escherichia coli. Bleriot C, Effantin G, Lagarde F, Mandrand-Berthelot MA, Rodrigue A; J Bacteriol. 2011;193:3785-3793. PMID:21665978