Activation of the Cpx phosphorelay signal transduction system in acidic phospholipid-deficient pgsA mutant cells of Escherichia coli

► The Escherichia coli pgsA gene is responsible for acidic phospholipid synthesis. ► The pssA gene is responsible for zwitterionic phospholipid synthesis. ► Not only the Rcs system but also the Cpx system is activated in a pgsA mutant. ► The Cpx system, but not the Rcs system, is activated in a pssA mutant. ► Lipoprotein maturation defect in a pgsA mutant is not involved in Cpx activation.