Serine/threonine kinase (pk-1) is a component of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) very late gene transcription complex and it phosphorylates a 102 kDa polypeptide of the complex.

The baculovirus gene, protein kinase-I (pk-1) encodes a serine/threonine kinase that is essential for very late gene expression. Late and very late genes of the baculoviruses are transcribed by an alpha-amanitin resistant RNA polymerase. The very late gene promoter transcription initiation complex was isolated from nuclei of Autographa californica multiple nucleopolyhedrovirus (AcMNPV)-infected Sf9 cells by DNA affinity purification and found to contain 4 major polypeptides of sizes approximately 102, 38, 32, and 18 kDa. The 32 kDa polypeptide was immunoreactive to AcMNPV anti-pk-1 antibody and phosphorylated the 102 kDa polypeptide, earlier reported as late gene expression factor LEF-8. Electrophoretic mobility shift assays with anti-pk-1 antibody indicated the binding of promoter DNA with recombinant AcMNPV-pk-1 and transcription initiation complex proteins. All these results suggested AcMNPV-pk-1 to be a component of the viral very late gene transcription initiation complex.