Mutagenic analysis of potato virus X movement protein (TGBp1) and the coat protein (CP): in vitro TGBp1-CP binding and viral RNA translation activation.
Previously, we have shown that encapsidated Potato virus X (PVX) RNA was non-translatable in vitro, but could be converted into a translatable form by binding of the PVX movement protein TGBp1 to one end of the virion or by coat protein (CP) phosphorylation. Here, a mutagenic analysis of PVX CP and TGBp1 was used to identify the regions involved in TGBp1-CP binding and translational activation of PVX RNA by TGBp1. It was found that the C-terminal (C-ter) 10/18 amino acids region was not essential for virus-like particle (VP) assembly from CP and RNA. However, the VPs assembled from the CP lacking C-ter 10/18 amino acids were incapable of TGBp1 binding and being translationally activated. It was suggested that the 10-amino-acid C-ter regions of protein subunits located at one end of a polar helical PVX particle contain a domain accessible to TGBp1 binding and PVX remodelling. The non-translatable particles assembled from the C-ter mutant CP could be converted into a translatable form by CP phosphorylation. The TGBp1-CP binding activity was preserved unless a conservative motif IV was removed from TGBp1. By contrast, TGBp1-dependent activation of PVX RNA translation was abolished by deletions of various NTPase/helicase conservative motifs and their combinations. The motif IV might be essential for TGBp1-CP binding, but insufficient for PVX RNA translation activation. The evidence to discriminate between these two events, i.e. TGBp1 binding to the CP-helix and TGBp1-dependent RNA translation activation, is discussed.
Zayakina
Olga
O
Department of Virology, Moscow State University, Moscow 119991, Russia.
Arkhipenko
Marina
M
Kozlovsky
Stanislav
S
Nikitin
Nikolai
N
Smirnov
Alexander
A
Susi
Petri
P
Rodionova
Nina
N
Karpova
Olga
O
Atabekov
Joseph
J
D020816:Amino Acid Motifs; D036022:Capsid Proteins / Q000235:genetics*; D016296:Mutagenesis; D010766:Phosphorylation; D053830:Plant Viral Movement Proteins / Q000235:genetics*; D017863:Potexvirus / Q000235:genetics* / Q000502:physiology; D011485:Protein Binding; D014176:Protein Biosynthesis; D012367:RNA, Viral / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D017384:Sequence Deletion; D019065:Virus Assembly
D036022:Capsid Proteins; D053830:Plant Viral Movement Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C058750:coat protein, Potato virus X