Neomycin Inhibits the Phosphatidylinositol Monophosphate and Phosphatidylinositol Bisphosphate Stimulation of Plasma Membrane ATPase Activity

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Abstract
The inositol phospholipids, phosphatidylinositol monophosphate (PIP) and phosphatidylinositol bisphosphate (PIP2), have been shown to increase the vanadate-sensitive ATPase activity of plant plasma membranes (AR Memon, Q Chen, WF Boss [1989] Biochem Biophys Res Commun 162: 1295-1301). In this paper, we show the effect of various concentrations of phosphatidyinositol, PIP, and PIP2 on the plasma membrane vanadate-sensitive ATPase activity. PIP and PIP2 at concentrations of 10 nanomoles per 30 microgram membrane protein per milliliter of reaction mixture caused a twofold and 1.8-fold increase in the ATPase activity, respectively. The effect of these negatively charged phospholipids on the ATPase activity was inhibited by adding the positively charged aminoglycoside, neomycin. Neomycin did not affect the endogenous plasma membrane ATPase activity in the absence of exogenous lipids.