Figure 9.

Binding of CTX-A to Erd2p of Golgi membranes from Sf9 cells is not affected by antibodies directed against the cytoplasmic tail of Erd2p. Erd2p was overexpressed in Sf9 cells using Bacculovirus infection. Golgi membranes from overexpressing Sf9 cells were prepared and permeabilized as given in the Materials and Methods section and incubated at pH 7.2 with preimmune serum, antiserum directed against the cytoplasmic tail of Erd2p, or without serum. The pH was then adjusted to 6.0 and the binding of increasing concentrations of ¹²⁵I–CTX-A was measured. Blanks without membranes (ranging from ∼200 dpm to ∼1,800 dpm for the different concentrations of labeled CTX-A used) were subtracted. The binding curves obtained after the three different preincubation conditions show only minor (<5%) differences.