Figure 3.

The product of the LBP1 gene is an LCBP phosphatase. (A) LCBP-phosphatase activity was measured in wild-type (WT) W303-1A, Δlbp1, Δlbp2, and W303 cells carrying LBP1 or LBP2 on multicopy YEp plasmids by using phytosphingosine-1-³²P as substrate. (B) Effects of lipids and phosphatase inhibitors on LCBP-phosphatase activity of wild-type W303 cells (open bars) and the LBP1 overexpressor strain (hatched bars). The following agents were used: Triton X-100, 0.05%; hexadecylphosphate (100 μM); tartrate (10 mM); propanolol (4 mM); N-ethylmaleimide (NEM, 5 mM); phosphoethanolamine (10 mM); phosphoserine (10 mM); pyrophosphate (10 mM); glycerol 3-phosphate (6 mM); and NaF (10 mM). (C) Inhibition of LCBP-phosphatase activity by 100 μM concentrations of the indicated lipids in membrane fractions from the LBP1 overexpressor strain using phytosphingosine-1-³²P (open bars) or sphingosine-1-³²P (hatched bars) as substrates.