Structure, Dynamics and Functional Implications of the Eukaryotic Vault Complex

Vault ribonucleoprotein particles are naturally designed nanocages, widely found in the eukaryotic kingdom. Vaults consist of 78 copies of the major vault protein (MVP) that are organized in 2 symmetrical cup-shaped halves, of an approximate size of 70x40x40 nm, leaving a huge internal cavity which accommodates the vault poly(ADP-ribose) polymerase (vPARP), the telomerase-associated protein-1 (TEP1) and some small untranslated RNAs. Diverse hypotheses have been developed on possible functions of vaults, based on their unique capsular structure, their rapid movements and the distinct subcellular localization of the particles, implicating transport of cargo, but they are all pending confirmation. Vault particles also possess many attributes that can be exploited in nanobiotechnology, particularly in the creation of vehicles for the delivery of multiple molecular cargoes. Here we review what is known about the structure and dynamics of the vault complex and discuss a possible mechanism for the vault opening process. The recent findings in the characterization of the vaults in cells and in its natural microenvironment will be also discussed.