Measles and Nipah virus assembly: Specific lipid binding drives matrix polymerization.

Measles virus, Nipah virus, and multiple other paramyxoviruses cause disease outbreaks in humans and animals worldwide. The paramyxovirus matrix (M) protein mediates virion assembly and budding from host cell membranes. M is thus a key target for antivirals, but few high-resolution structures of paramyxovirus M are available, and we lack the clear understanding of how viral M proteins interact with membrane lipids to mediate viral assembly and egress that is needed to guide antiviral design. Here, we reveal that M proteins associate with phosphatidylserine and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2 ] at the plasma membrane. Using x-ray crystallography, electron microscopy, and molecular dynamics, we demonstrate that PI(4,5)P 2 binding induces conformational and electrostatic changes in the M protein surface that trigger membrane deformation, matrix layer polymerization, and virion assembly.