Figure 3.

In vitro (A,B) assembly and (C,D) disassembly reactions with HBV capsids that exemplify defects in icosahedral symmetry. Without external information, one would not know that in both reactions T = 4 particles missing about 30 of the expected 120 dimers are prevalent. (A) Cryo-micrographs of HBV assembly reactions that were stalled due to conditions led to strong association energy and depletion of capsid protein. The micrograph shows normal T = 4 particles (white), disrupted T = 4 particles (red), and a T = 3 particle (black). The scale bar is 50 nm. (B) In reference free 2D class averages of T = 4 capsids from micrographs such as (A), the periphery of every class is disrupted, indicating that defects in particles dominate classification. The disrupted regions in the displayed classes are identified by the dashed red arcs. (C) Individual images from a negative stain electron micrograph of HBV capsids in a dissociation reaction induced by 1.2 M urea. Particle morphology was preserved by embedding in 0.1% trehalose. Many of these particles had “tails”, probably density from subunits falling off of capsids. (D) The first eight classes (in order of prevalence). Most classes are typical of T = 4 particles and display no obvious defects. Class 2 (blue box) is a T = 3 particle which make up about 10% of the total. Class 3 has an elliptical morphology not typically seen in HBV. Panels A and B are from Pierson et al. [20], and Panels C and D are from Lee et al. [53]. Figures are used with permission.