The nucleoprotein of Marburg virus is phosphorylated.

The nucleoprotein (NP) of Marburg virus (MBG), a filovirus, is encoded by the gene closest to the 3' end of the non-segmented negative-strand RNA genome. Sequence comparison has indicated that NP is the functional equivalent to the nucleoproteins of paramyxoviruses and rhabdoviruses. Expression of recombinant NP in two eukaryotic systems using vaccinia virus and baculovirus (vectors pSC11 and pAcYMB1, respectively) and analysis of MBG-specific proteins have demonstrated that the NP of MBG is phosphorylated. The NP appeared in two forms differing in M(r) by about 2K (94K and 92K respectively). Dephosphorylation clearly demonstrated that the 94K form is phosphorylated whereas the 92K form is unphosphorylated. In virion particles NP was exclusively present in the phosphorylated form. These findings suggest that only the phosphorylated NP can form nucleocapsid complexes and interact with the genomic RNA.