Phosphorylation of myelin basic protein by vaccinia virus cores

Abstract

PROTEIN kinases, catalysing the transfer of the γ phosphate from ATP to serine and threonine residues in protein substrates have been described in several enveloped viruses1–3. Vaccinia virus contains a protein kinase that has recently been well characterised4: it is located within the viral core, is not stimulated by cyclic mononucleotides and phosphorylates at least two viral acceptor proteins. The biological functions of the protein kinase and acceptor proteins are unknown, but it is possible that the viral protein kinase could also act on host proteins, thus providing a mechanism by which the virus could modify or control host processes on infection1. Vaccinia virus can induce a demyelinisation after experimental infection, but the mechanism for this is poorly understood5. It has been suggested that direct viral action on membranes may have a role in the pathogenesis of virus-induced demyelinisation6. We have therefore investigated the ability of vaccinia virus cores to phosphorylate human myelin membranes in an in vitro system and report here that they can phosphorylate purified myelin basic protein as well as basic protein in the myelin sheath.