Rescue of maturation-defective flock house virus infectivity with noninfectious, mature, viruslike particles.

The infectivity of flock house virus (FHV) requires autocatalytic maturation cleavage of the capsid protein at residue 363, liberating the C-terminal 44-residue gamma peptides, which remain associated with the particle. In vitro studies previously demonstrated that the amphipathic, helical portion (amino acids 364 to 385) of gamma is membrane active, suggesting a role for gamma in RNA membrane translocation during infection. Here we show that the infectivity of a maturation-defective mutant of FHV can be restored by viruslike particles that lack the genome but undergo maturation cleavage. We propose that the colocalization of the two defective particle types in an entry compartment allows the restoration of infectivity by gamma.