Herpes simplex virus-encoded ribonucleotide reductase: evidence for the dissociation/reassociation of the holoenzyme.

35S-labeled cells infected with herpes simplex virus type 1 (HSV-1), temperature-sensitive (ts) mutant ts 1222 were used as a source of the large subunit of the viral ribonucleotide reductase (RR) to investigate the binding of the large (RR1) and small (RR2) subunits in the active enzyme. Mixing 35S-labeled RR1 from ts 1222 with unlabeled RR1/RR2 complex from wild type (wt) infected cells resulted in the formation of a complex between 35S-labeled RR1 and unlabeled RR2, indicating that the complex between the RR1 and RR2 subunits is dynamic and subunit dissociation/reassociation occurs during enzyme function. Similar results were obtained when unlabeled HSV-2 RR was substituted for HSV-1 RR, demonstrating that the holoenzyme can be formed the large subunit of HSV-1 RR and the small subunit of HSV-2.