Phosphorylation of Marburg virus VP30 at serines 40 and 42 is critical forits interaction with NP inclusions

The Marburg virus (MBGV) nucleocapsid complex is composed of four viral pro teins (NP, L, VP35, and VP30) and the negative-strand nonsegmented genomic RNA. NP, L, and VP35 are functionally conserved among the order Mononegavir ales, whereas VP30, a phosphoprotein, represents a filovirus-specific nucle ocapsid protein. In the present paper, we have characterized the localizati on and function of VP30 phosphorylation. The main phosphorylation sites are represented by seven serine residues in the region of amino acid 40 to 51 of VP30. Additionally, trace amounts of phosphothreonine were detected. Sub stitution of serine residues 40 and 42 by alanine abolished the interaction of VP30 with NP-induced inclusion bodies, which contain nucleocapsid-like structures formed by NP. Substitution of the other phosphoserine residues h ad little effect on this interaction. Replacement of the introduced alanine residues 40 and 42 by aspartate restored the interaction between VP30 and the NP inclusions pointing to the importance of negative charges at these p articular positions. (C) 2001 Academic Press.