Plays an essential role virus particle assembly and budding. Promotes virus assembly and budding by interacting with host proteins of the multivesicular body pathway. The interaction with host E3 ubiquitin ligase SMURF2 facilitates virus budding (By similarity). The interaction with the nucleocapsid and the plasma membrane may also facilitate virus budding. Specific interactions with membrane-associated GP and VP24 during the budding process may also occur (By similarity). May play a role in genome replication (By similarity). Exists as a dimer until it reorganizes at the plasma membrane into multimeric form. Interacts with host TSG101. Interacts (via PPXY motif) with SMURF2 (via WW domains); the interaction positively regulates virus budding. In virion, localizes on the intravirional side of the membrane. In the host cell, it is found associated with virus-induced membrane proliferation foci and probably also in multivesicular bodies. These VP40-enriched membrane clusters are then redistributed to the plasma membrane where budding takes place. Late-budding domains (L domains) are short sequence motifs essential for viral particle budding. They recruit proteins of the host ESCRT machinery (Endosomal Sorting Complex Required for Transport) or ESCRT-associated proteins. VP40 contains one L domain: a PPXY motif which potentially interacts with the WW domain 3 of NEDD4 E3 ubiquitin ligase and the three WW domains of SMURF2 E3 ubiquitin ligase. Most abundant protein in the virion. Belongs to the filoviridae matrix protein VP40 family.