| 内容提要: |
Protein capsids represent a promising class of nanoscale container for the storage and delivery of molecular cargoes. Their hollow supramolecular structures and high degree of symmetry provide a scaffold that can be readily modified by genetic or chemical methods. The capsid formed by Aquifex aeolicus lumazine synthase (AaLS) is built from 60 identical monomers that assemble as a docamer-of-pentamers and is an attractive starting point for engineering new drug delivery systems. Here we report the loading of an AaLS variant (called AaLS-IC) with the amino acid selenocysteine, a model drug with reported cytotoxic activity against hepatoma cells. AaLS-IC, which contains a single cysteine per subunit that projects into the capsid interior, was modified by reaction with selenocystine to generate a selenosulfide conjugate between the capsid and selenocysteine. We show that selenocysteine can be loaded into the AaLS-IC capsid with a 98% yield. Further, we are making a derivative of selenocystine in which the α-amino group is modified with a coumarin dye, which will also be loaded into AaLS-IC capsids as a means to visualize drug release and intracellular trafficking. The ability of the AaLS-IC capsid to deliver selenocysteine or dye-modified selenocysteine into cells will be assessed by a combination of cytotoxicity and cell uptake studies. |