Extended Data Fig. 1: Schematic of the Gag cleavage cascade and current model of MA interactions at the plasma/viral membrane.

a, Schematic illustration of the Gag proteolytic cleavages that occur during HIV-1 maturation. Cleavages are ordered by relative rate as measured in-vitro⁶⁹. Virus schematics adapted from Briggs and Kräusslich (2011)⁷⁰ b, MA in the cytoplasm can bind tRNA (green) via the side pocket. MA binds to PtdIns(4,5)P₂ (PIP₂) (blue lipid) and cholesterol rich domains on the plasma membrane during viral assembly. This binding is facilitated by the insertion of a previously sequestered myristoyl group (yellow) and by electrostatic interactions at the HBR. Bound tRNA sterically prevents membrane binding of MA, thus tRNA^Lys3 is released upon membrane binding, leaving the side pocket unoccupied. The current model, based on data from NMR¹² and our previous cryo-ET study¹, is that that upon maturation, MA partially extracts molecules of PtdIns(4,5)P₂ from the inner leaflet of the viral membrane, binding the phosphatidylinositol head group and one of the acyl tails within the side pocket. This aspect of the model is, however, contradicted by the findings of this study (indicated by red cross).