Budded Autographa californica NPV 64K protein: Further biochemical analysis and effects of postimmunoprecipitation sample preparation conditions

Previously it was shown that AcV(1), a neutralizing monoclonal antibody of the Autographs californica nuclear polyhedrosis virus-budded phenotype reacted with a surface antigen present on infected cells during virus budding, and in the viral envelope (L. E. Volkman, P. A. Goldsmith, R. T. Hess, and P. Faulkner (1984), Virology133, 354–362). Radioimmune precipitation of solubilized, [(35)S]methionine-labeled budded virus with AcV(1) and analysis on SDS-PAGE revealed four bands consistently: one major band at 64,000 Da, and three minor bands at 127,000, 59,000, and 49,000 Da. The reason for the appearance of four bands instead of one was unclear. Data suggest that two of the bands, 49K and 59K, are aberrant, and are the products of sample preparation conditions. Further, evidence is presented that the 127K band is composed of dimers of the 64K protein, and that under nonreducing conditions, oligomers (trimers and tetramers) of 64K protein can also be detected. BVGP 64 is additionally shown to be phosphorylated and to have an isoelectric point of 3.15. The BVGP 64 epitope reactive with AcV(1) is destroyed by interaction with SDS. This could account for the lack of neutralizing activity of antiserum made to the SDS-PAGE purified BVGP 64.