Fig. 4: 2D crystallography of HIV-1 MA shows SP2 binding in vitro.

a–c, Example 2D class averages of MA assembled on lipid monolayers with or without addition of SP2 showing mature (a,b) and immature (c) arrangements. d, Quantification of particles that were identified as either mature (M) or immature (I) MA lattices by 2D classification. A total of 139,500 particles were picked initially for each experiment. Error bars indicate mean ± s.d. between three experiments. e,f, An extra density in the side binding pocket of MA highlighted by the dashed square is visible in the +SP2 2D class average (f). g,h, Simulated projections of cryo-EM density map of the MA from MASP1 HIV-1 cleavage mutant. The side pocket density corresponding to SP2 was removed in the structure used to generate g to simulate the absence of the SP2 peptide.