Maturation of the matrix and viral membrane of HIV-1
Gag - the main structural protein of HIV-1 - is recruited to the plasma membrane for virus assembly by its matrix (MA) domain. Gag is subsequently cleaved into its component domains, causing structural maturation to repurpose the virion for cell entry. We determined the structure and arrangement of MA within immature and mature HIV-1, providing a basis to understand MAs role in virus assembly. Unexpectedly, we found that MA rearranges during maturation, to form a new, hexameric lattice in which the acyl chain of a phospholipid extends out of the membrane to bind a pocket in MA. Our data suggest that proteolytic maturation of HIV-1 not only achieves assembly of the viral capsid surrounding the genome, but extends to repurpose the membrane-bound MA lattice for an entry or post-entry function, and causes partial removal of 2,500 acyl chains from the viral membrane.