9.B.20.1.4
Magnesium uptake system of 215 aas and 4 or 5 TMSs, YhiD (YhhE; MgtC).  This protein seems to be a low affinity magnesium uptake protein that could function either as a channel or a carrier (Ishijima et al. 2015). It plays a role in acid resistance at high cell densities together with the 6 TMS HdeD protein that may be an organic acid exporter (TC# 9.B.36.1.1) (Mates et al. 2007). The mgtC gene, which is present in S. enterica but not in E. coli, is responsible for the differences in RpoS accumulation between these two bacterial species. Thus, bacteria possess a mechanism to control RpoS accumulation responding to cytoplasmic Mg²⁺ levels, the difference of which causes distinct RpoS accumulation in closely related bacterial species (Park et al. 2018).