FIGURE 1.

A. Immunoprecipitation of ³⁵S-Methionine-labeled GP64 constructs with MAb AcV1 (lanes 1–6) and anti c-Myc (lanes 7–8). Cells expressing wild-type AcMNPV or NTr1(21-512) GP64 proteins were metabolically labeled with ³⁵S-Methionine. Cell lysates containing wild type GP64 or NTr1(21-512) proteins were subjected to various treatments (pH 6.2, pH 4.5, or pH 4.5 followed by a shift to 6.2), then subjected to immunoprecipitation with MAb AcV1 or anti c-Myc, and analyzed on an SDS-10% polyacrylamide gel. The diagram (bottom) shows the construction of a control protein, N-terminally cMyc tagged GP64, NTr1(21-512). (SP, signal peptide; cMyc, cMyc tag; TM, transmembrane domain; CTD, cytoplasmic tail domain)

B. Effect of low pH treatment on BV infectivity. Wild type AcMNPV budded viruses at pH 6.2 were adjusted to pH 4.5 with either PBS (pH 1.7) or Grace’s medium (pH 2.1). The low pH adjusted virus was incubated for 30 min at room temperature, then returned to pH 6.2 by addition of either PBS (pH 12.3) or Grace’s medium (pH 9.6). Titres were then determined by end-point dilution. Control BV preparations were similarly treated with PBS or Grace’s medium but at pH 6.2 only. The results represent the average value of three separate replicate experiments.