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. Author manuscript; available in PMC: 2023 Sep 1.
Published in final edited form as: Nat Struct Mol Biol. 2023 Jan 9;30(3):370–382. doi: 10.1038/s41594-022-00887-4

Figure 8. The HIV-1 immature lattice enriches IP6 into virions to catalyse mature capsid assembly.

Figure 8

The immature lattice does not intrinsically need IP6 for assembly but instead acts as a ‘net’ to capture IP6 from producer cells and enrich it into virions. Virions that have budded from the cell undergo maturation during which the immature lattice is cleaved by the viral protease. This results in the liberation of CA protein from Gag and the release of IP6 from its binding site in the immature Gag lattice. The newly freed IP6 promotes the assembly of CA into capsomers (predominately hexamers but also pentamers), which are used to construct the conical capsid characteristic of mature HIV-1 particles. Because maturation happens inside virions, separated from the cell, if there are insufficient IP6 molecules packaged into virions then stable mature capsids cannot form and the resulting HIV-1 particles fail to become infectious.