Fig. 4.
TRIM5-21R assembly is promoted by preformed, stabilized two-dimensional CA-NCA14C/E45C/W184A crystals that mimic the surface of the HIV-1 capsid. (A) Representative EM image of a CA-NC/TRIM5-21R cocrystal (1∶1 molar protein ratio, 24 h incubation). (B) Expanded view of the region boxed in red in (A). The contrast was stretched using Adobe Photoshop to enhance the clarity of the TRIM5-21R hexagons. (C) EM image of CA-NC alone at the same magnification as (B), shown for comparison. Scale bars,100 nm. (D) and (E) Computed Fourier transforms of the crystals shown in (B) and (C), respectively. In (D), diffraction from the TRIM5-21R lattice is evident (circled in green). Note that in this case, there are at least two stacked TRIM lattices (the first-order reflections of each correspond to a hexagonal lattice with ∼350 Å spacing), and at least three stacked CA lattices (a = 93.1 Å, b = 93.1 Å, and γ = 119.0°; a = 92.5 Å, b = 94.2 Å, and γ = 118.9°; a = 93.1 Å, b = 92.6 Å, and γ = 118.8°). The TRIM and CA diffraction patterns do not overlap in spatial frequency owing to the size of the TRIM lattice and its lack of long-range order. As expected, TRIM diffraction is absent in the transform of CA-NC alone, which shows two CA lattices (E).