SUBUNIT PROTEIN AND ALKALINE PROTEASE OF ENTOMOPOXVIRUS SPHEROIDS

The inclusion body (spheroid) matrix of Choristoneura biennis (Free.) entomopoxvirus is composed of a single subunit protein termed spheroidin. This protein has a molecular weight of 102,000 when extracted by detergent disruption of spheroids in 8 M urea. These conditions inhibit an alkaline protease activity which we have detected in the spheroids. The enzyme has an optimum pH range of 10 to 11. It is heat labile, in that 90% of the activity is destroyed by heating at 60° for 10 min, and is inhibited by soybean trypsin inhibitor, sodium dodecyl sulfate and mercuric ion. Activation of the protease during extraction by alkaline dissolution of the spheroids or by detergent disruption in the absence of 8 M urea results in the breakdown of the spheroidin subunit into discreet peptides. © 1979.