When membranes isolated from an unsaturated fatty acid auxotroph of Escherichia coli grown on oleate were treated with aqueous acetone, approximately 50% of the phospholipids were removed and 70% of the succinic-dichloroindophenol (DCI) reductase activity was lost. Preliminary incubation with total lipids isolated from cells grown on oleate or elaidate restored the reductase activity to the acetone-treated membrane. An Arrhenius plot of the activity remaining in oleate membranes after delipidation showed no discontinuity between 12–37°. When the same membrane preparation was previously incubated with dispersions of lipids, the Arrhenius plot of succinic-DCI reductase activity showed a discontinuity at 19° when oleate lipids were used, and at 28° when elaidate lipids were used. Total cell lipids could be replaced with phospholipids plus coenzyme Q6. However, neither of these alone had a significant stimulatory effect. The Arrhenius plot of succinic-ubiquinone reductase activity of either oleate acetone-extracted membranes or elaidate acetone-extracted membranes gave transitions between 27–29° after preliminary incubation with elaidate phospholipids plus Q6, and between 17–19° after prior incubation with oleate phospholipids plus Q6. The data indicate that the presence of a transition in Arrhenius plot of succinic dehydrogenase (measured by DCI reduction) in the membranes of this mutant is dependent on the phospholipids, and that the temperature at which this transition occurs is determined by the nature of the apolar group of the lipid.
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 25 Nov 1972|