The protein subunits of the double-stranded RNA dependent RNA polymerase and methyltransferase of the cytoplasmic polyhedrosis virus of silkworm, Bombyx mori.

The particles of CPV of silkworm contain double-stranded RNA polymerase and methyltransferase. It was reported in a previous paper that the genome-enzyme complex could be isolated. The genome-enzyme complex shows high enzyme activity of RNA polymerase and methyltransferase in spite of the fact that it consists of only 5 percent of the protein. In order to clarify the protein subunits of the RNA polymerase and methyltransferase, two methods were adopted. The SDS-polyacrylamide gel electrophoretogram showed that the 125I-labeled genome-enzyme complex of CPV contained three protein components in molecular weight of 33 K, 67 K and 142 K daltons respectively and each protein component of them consisted of more than two protein subunits with different isoelectric points in 2-dimensional electrophoretogram. The antibody to the five protein components (P1, P2, P3, P4, P5) was prepared and used to inhibit the enzyme activities of RNA polymerase and methyltransferase. It showed that the RNA polymerase was inhibited by the antibody to proteins P1, P2 and P4, whereas the methyltransferase was mainly inhibited by the antibody to protein P1.