Escherichia coli CorA-Salmonella typhimurium ZntB_like family
A family of the MIT superfamily of essential membrane proteins involved in transporting divalent cations (uptake or efflux) across membranes. Members of this family are found in all three kingdoms of life. It is a functionally diverse family, including the Mg2+ transporters Escherichia coli and Salmonella typhimurium CorAs (which can also transport Co2+, and Ni2+ ), and the Zn2+ transporter Salmonella typhimurium ZntB which mediates the efflux of Zn2+ (and Cd2+). It also includes two Saccharomyces cerevisiae members: the inner membrane Mg2+ transporters Mfm1p/Lpe10p, and Mrs2p, and a family of Arabidopsis thaliana members (AtMGTs) some of which are localized to distinct tissues, and not all of which can transport Mg2+. Structures of the intracellular domain of Vibrio parahaemolyticus and Salmonella typhimurium ZntB form funnel-shaped homopentamers, the tip of the funnel is formed from two C-terminal transmembrane (TM) helices from each monomer, and the large opening of the funnel from the N-terminal cytoplasmic domains. The GMN signature motif of the MIT superfamily occurs just after TM1, mutation within this motif is known to abolish Mg2+ transport through Salmonella typhimurium CorA, and Mrs2p. Natural variants such as GVN and GIN, such as occur in some ZntB family proteins, may be associated with the transport of different divalent cations, such as zinc and cadmium. The functional diversity of MIT transporters may also be due to minor structural differences regulating gating, substrate selection, and transport.
Comment:based on Thermotoga maritima CorA and on partial structures: the intracellular domains of Vibrio parahaemolyticus and Salmonella typhimurium ZntB; contacts at 4A
Jiyao W et al.(2023). "The conserved domain database in 2023.",