Proteolytic cleavage of polyhedral protein during dissolution of inclusion bodies of the nuclear polyhedrosis viruses of Bombyx mori and Galleria mellonella under alkaline conditions

Inclusion bodies (IB) of nuclear polyhedrosis viruses (NPV) of Bombyx mori and Galleria mellonella were dissolved in 67% acetic acid and in sodium carbonate solution at pH 11.0. The polyhedral protein preparations obtained in this way were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by ultracentrifugation. The polyhedral proteins of B. mori and G. mellonella NPV obtained by dissolving IB in acetic acid were shown to have mainly one component with a molecular weight of about ± 28,000 and sedimentation coefficients in 0.1 M NaOH of 1.8 and 2.1 S, respectively. During dissolution of IB in alkaline condition, both the proteins are cleaved and reveal several components. The quantity and the ratio of the components depend on the duration of storing and on the temperature during the dissolution of IB and on the stage of insect development at the time of IB isolation. It is suggested that the cleavage of IB protein is a result of alkaline proteinase(s) activity.