FIG. 3.

Electron micrographs of mutant virions with reduced infectivity. (A) Shown are overviews over fields of virions photographed at ×50,000 to demonstrate variability of capsid shapes (top panels) and particle morphologies resulting from CA mutations in the NTD (middle panels) and CTD (bottom panels). Mutants with phenotypes are ordered from the N to C terminus except for those that produced gross defects (shown in Fig. 3B and C). (B) Mutant virions with gross particle assembly defects. (C) Cell-associated Gag assemblies with gross defects in particle formation. Shown are CA E75A/E76A and K158A mutants expressed in 293T cells (upper panels and lower right) and CA K158A mutant expressed in HeLa cells (lower left). Note the aberrant curvature produced by Gag molecules assembling beneath the plasma membrane. Scale bars in all figures are 100 nm.