Figure 3.

Plasma Membrane PtdInsP 5-Kinase–Specific Activity and PtdIns(4,5)P₂ Levels Increased >100-Fold in Hs PIPKIα Lines and Was Not Associated with Actin.

(A) and (B) The plasma membrane (PM)–enriched fraction from wild-type and two different lines of transgenic tobacco cells were analyzed for PtdInsP 5-kinase activity without (A) and with (B) added substrate, PtdIns(4)P.

(C) The PtdInsP 5-kinase activity recovered with F-actin polymerized and recovered in a 20,000g pellet from the plasma membrane of NT-1 and Hs PIPKIα lines was compared.

(D) Mass measurements of plasma membrane PtdIns(4,5)P₂ levels of wild-type and Hs PIPKIα lines. The values plotted are the averages ± sd of two to three independent experiments assayed in duplicate. Note the data in (B) and (D) are plotted on a log scale.