Structural characterization and membrane binding properties of the matrix protein VP40 of Ebola virus

The matrix protein VP40 of Ebola virus is believed to play a central role i n viral assembly as it targets the plasma membrane of infected cells and su bsequently forms a tightly packed layer on the inner side of the viral enve lope. Expression of VP40 in Escherichia coli and subsequent proteolysis yie lded two structural variants differing by a C-terminal truncation 114 amino acid residues long. As indicated by chemical cross-linking studies and ele ctron microscopy, the larger polypeptide was present in a monomeric form, w hereas the truncated one formed hexamers. When analyzed for their in vitro binding properties, both constructs showed that only monomeric VP40 efficie ntly associated with membranes containing negatively charged lipids. Membra ne association of truncated, hexameric VP40 was inefficient, indicating a m embrane-recognition role for the C-terminal part. Based on these observatio ns we propose that assembly of Ebola virus involves the formation of VP40 h examers that is mediated by the N-terminal part of the polypeptide. (C) 200 0 Academic Press.