Myristylation and polylysine-mediated activation of the protein kinase domain of the large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10)

The amino-terminal domain of the large subunit of herpes simplex virus type 2 (HSV-2) ribonucleotide reductase (ICP10) was previously shown to possess protein kinase (PK) activity that localizes to the cytosolic, cytoskeletal, and plasma membrane fractions. Further studies of the PK domain using computer-assisted sequence analysis have identified a single transmembrane segment and fatty acid incorporation findings indicate that ICP10 is myristylated. Myristylation does not depend on a viral enzyme, since myristic acid is incorporated into ICP10 precipitated from cells transfected with an ICP10 expression vector. It is also incorporated into the 57-kDa protein expressed by the amino-terminal PK expression vector. The myristyl moiety is linked through an amide bond. The basic protein polylysine stimulates the kinase activity and alters its divalent cation requirements resulting in 20- to 40-fold stimulation in the presence of 0.1 mM Mn2+. The PK activity is inhibited by antibody to synthetic peptides corresponding to residues 355-369 and 13-26, respectively, located within, and amino-terminal to, the predicted PK catalytic domain.