FIG. 3.

Structural analysis of p32k and LH3 mutants. (A) Surface view of p32k knockout virus along the three-fold axis at ∼28-Å resolution (0.5 FSC criterion; data not shown) showing the presence of the “knob-like” densities corresponding to LH3 (blue). The diameter of this particle is ∼94 nm. Scale bar, 15 nm. (B) Negative-stain images of LH3 mutant viruses. More than 95% of the viruses dissociated, as revealed by the smaller size of the remaining particles (diameter of ∼85 nm; blue arrow) and the many hexon subunits (white arrow) and fiber proteins bound to the penton complexes (yellow arrow) that are clearly seen in the background. Scale bar, 80 nm. The few intact viruses (red arrow) are larger (94 nm diameter) and have radially protruding fibers (two of which are indicated by black arrows). (C) High-magnification image of individually shed fiber/penton complexes (black arrow). What appears to be the attached penton complex and fiber head domain have been marked (red and yellow arrows, respectively). Scale bar, 18 nm.