Anionic phospholipids in the control of the membrane surface potential in Escherichia coli: their influence on transport mechanisms.

1. Phosphatidylserine (PS)-rich Escherichia coli cells were utilized to investigate the role of anionic phospholipids on membrane surface potential and their effect upon active transport mechanisms. 2. It was found that: 3. The transport of inorganic phosphate and glutamate, which depends upon cations, was increased (Km decreases) in PS-rich cells as compared to normal cells. 4. The reduction of the negative surface potential by MgCl2 or by the cationic local anesthetic procaine, brought about a decrement in the uptake of both substrates. 5. When the negative surface potential of the PS-rich cells was reduced, the Km returned back to the values found in normal cells. 6. A direct correlation between the ratio anionic/zwitterionic phospholipids, negative surface potential and increment in the initial rate of transport was found.