Tetramerization is a conserved feature of the virion-associated protein inplant pararetroviruses

All plant pararetroviruses belong to the Caulimoviridae family. This family contains six genera of viruses with different biological, serological, and molecular characteristics. Although some important mechanisms of viral rep lication and host infection are understood, much remains to be discovered a bout the many functions of the viral proteins. The focus of this study, the virion-associated protein (VAP), is conserved among all members of the gro up and contains a coiled-coil structure that has been shown to assemble as a tetramer in the case of cauliflower mosaic virus. We have used the yeast two-hybrid system to characterize self-association of the VAPs of four dist inct plant pararetroviruses, each belonging to a different genus of Caulimo viridae. Chemical cross-linking confirmed that VAPs assemble into tetramers . Tetramerization is thus a common property of these proteins in plant para retroviruses. The possible implications of this conserved feature for VAP f unction are discussed.