A Role for the acrA Gene in the Protection of Escherichia coli Cells against Excess Sodium

概要

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The acrA gene determines the sensitivity of Escherichia coli K-12 cells to acriflavine, which is one of the acridine dyes and which effectively eliminates certain plasmids from the bacterial cells. The acriflavine-sensitivity mutation leads to instability of plasmids, such as sex (F)- and drug-resistance (R)-factors and to loss of a membrane protein with molecular weight about 60 kDa (Nakamura 1974, 1976, Nakamura et al. 1975, 1981). We have found that cells with a mutant acrA gene were also more sensitive to an excess of sodium ions in the medium than were the wild-type acrA^+ cells (Nakamura 1977). The product of the acrA gene hindered the accumulation of sodium by the cells. Although mutations in the proA or proB genes, which determine the synthesis of the enzymes γ-glutamyl phosphate reductase and γ-glutamyl kinase, respectively, in the proline-biosynthetic pathway also led to sensitivity to and accumulation of excess sodium, the presence of the acrA^+ allele decreased both these parameters.