(375c) Crosslinked, Self-Assembled Protein Nanocapsules

Self-assembled ribonucleoprotein nanocapsules, called vaults, may serve as useful compartments for material encapsulation. Vaults exist naturally in almost all eukaryotes, and their dimensions (72.5 x 41 x 41 nm), hollow interior, and ability to be taken up by mammalian cell lines give them the potential to be used as drug delivery vehicles. They also have been reported to dissociate into two halves which further open into two flower-like structures when deposited on polylysine-coated mica surfaces. This triggered conformational change prompted us to further investigate the manipulation of vault conformation using various methods.

Intact vaults are also capable of dynamic structural change in solution to allow for entry of external material. Previously, we have used multiangle laser light scattering, fluorescence spectroscopy, quartz crystal microbalance, and transmission electron microscopy to demonstrate that vaults dissociate into half vault structures when exposed to low pH conditions. However, intact vaults still allow the entry of rather large molecules due to dynamic structural change behavior. In order to successfully utilize vaults as vehicles for encapsulated material, we have arrived at the use of various amine-reactive, crosslinking reagents to ensure rigidity of the vault structure. When crosslinked vaults are exposed to low pH conditions, they no longer dissociate into half vaults as shown by TEM images. Using a reducible crosslinking reagent, the cross-linked vaults can be opened to allow the release of encapsulated material. Current work includes comparing the accessibility of small proteins and protein-agarose beads into crosslinked and un-crosslinked vaults.