Mutagenic analysis of potato virus X movement protein (TGBp1) and the coat protein (CP): in vitro TGBp1-CP binding and viral RNA translation activation

Mol Plant Pathol. 2008 Jan;9(1):37-44. doi: 10.1111/j.1364-3703.2007.00445.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Capsid Proteins / genetics*
  • Mutagenesis
  • Phosphorylation
  • Plant Viral Movement Proteins / genetics*
  • Potexvirus / genetics*
  • Potexvirus / physiology
  • Protein Binding
  • Protein Biosynthesis*
  • RNA, Viral / genetics*
  • RNA-Binding Proteins / genetics
  • Recombinant Proteins / genetics
  • Sequence Deletion
  • Virus Assembly


  • Capsid Proteins
  • Plant Viral Movement Proteins
  • RNA, Viral
  • RNA-Binding Proteins
  • Recombinant Proteins
  • coat protein, Potato virus X