Structure of the mature P3-virus particle complex of cauliflower mosaic virus revealed by cryo-electron microscopy

J Mol Biol. 2005 Feb 11;346(1):267-77. doi: 10.1016/j.jmb.2004.11.052. Epub 2004 Dec 18.

Abstract

The cauliflower mosaic virus (CaMV) has an icosahedral capsid composed of the viral protein P4. The viral product P3 is a multifunctional protein closely associated with the virus particle within host cells. The best-characterized function of P3 is its implication in CaMV plant-to-plant transmission by aphid vectors, involving a P3-virion complex. In this transmission process, the viral protein P2 attaches to virion-bound P3, and creates a molecular bridge between the virus and a putative receptor in the aphid's stylets. Recently, the virion-bound P3 has been suggested to participate in cell-to-cell or long-distance movement of CaMV within the host plant. Thus, as new data accumulate, the importance of the P3-virion complex during the virus life-cycle is becoming more and more evident. To provide a first insight into the knowledge of the transmission process of the virus, we determined the 3D structures of native and P3-decorated virions by cryo-electron microscopy and computer image processing. By difference mapping and biochemical analysis, we show that P3 forms a network around the capsomers and we propose a structural model for the binding of P3 to CaMV capsid in which its C terminus is anchored deeply in the inner shell of the virion, while the N-terminal extremity is facing out of the CaMV capsid, forming dimers by coiled-coil interactions. Our results combined with existing data reinforce the hypothesis that this coiled-coil N-terminal region of P3 could coordinate several functions during the virus life-cycle, such as cell-to-cell movement and aphid-transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Caulimovirus / chemistry*
  • Caulimovirus / genetics
  • Caulimovirus / metabolism
  • Caulimovirus / ultrastructure*
  • Cryoelectron Microscopy*
  • Models, Molecular
  • Molecular Conformation
  • Virion / chemistry*
  • Virion / genetics
  • Virion / metabolism
  • Virion / ultrastructure*