RESUMO
Association of the reovirus proteins sigma 3 and mu 1 influences viral entry, initiation of outer capsid assembly, and modulation of the effect of sigma 3 on cellular translation. In this study, we have addressed whether structural changes occur in sigma 3 as a result of its interaction with mu 1. Using differences in protease sensitivity to detect conformationally distinct forms of sigma 3, we showed that association of sigma 3 with mu 1 caused a conformational change in sigma 3 that converted it from a protease-resistant to a protease-sensitive structure and occurred posttranslationally. The effect of mu 1 on the structure of sigma 3 was stoichiometric. Our results are consistent with a model in which sigma 3's association with mu 1 shifts its function from translational control to assembly of an outer capsid in which sigma 3 is folded into the protease-sensitive conformation that is required for its cleavage during the next round of infection.
Assuntos
Proteínas do Capsídeo , Capsídeo/metabolismo , Conformação Proteica , Proteínas de Ligação a RNA , Reoviridae/metabolismo , Serina Endopeptidases/metabolismo , Proteínas Virais/química , Proteínas Virais/metabolismo , Animais , Capsídeo/biossíntese , Capsídeo/química , Endopeptidase K , Cinética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/isolamento & purificação , Ligação Proteica , Biossíntese de Proteínas , Dobramento de Proteína , Coelhos , Reticulócitos/metabolismo , Transcrição Gênica , Proteínas Virais/biossíntese , Vírion/metabolismoRESUMO
Reovirus capsid protein delta 3 binds both double-stranded RNA (dsRNA) and zinc. Previous studies have revealed that the amino-terminal zinc finger is not required for the ability of delta 3 to bind dsRNA. We expressed wild-type and mutant delta 3 molecules by in vitro transcription/translation to evaluate the importance of the zinc finger for other functions of delta 3. delta 3 molecules with mutations in the zinc finger did not form complexes with capsid protein mu 1 but bound dsRNA more efficiently than wild-type delta 3 did. In contrast, a dsRNA-binding mutant was unimpaired in its ability to associate with mu 1. Studies with delta 3 fragments support these findings and indicate that sequences critical for delta 3's interaction with mu 1 lie in the amino terminus of the molecule. Our finding that mu 1 and dsRNA do not compete for identical binding sites on delta 3 has implications for its function as a translational regulator in infected cells.