The DNA binding protein from starved cells (SsDPS), isolated from Sulfolobus solfataricus, is a dodecameric protein cage belonging to the ferritin superfamily of proteins. It is naturally over-expressed in response to oxidative stress and also implicated in cellular DNA stabilization. Its outer shell diameter is 9 nm and interior diameter is 5 nm. While there are many self-assembled protein cage architectures that have been used as nanoscale materials the Dps protein cages are among the smallest. Here we report using SsDPS as a nanoscale container to encapsulate single copies of a peroxidase enzyme within the interior cavity of a chimeric DPS cage. DPS protein cages were purified and characterized to verify presence of peroxidase enzyme cargo. The catalytic activity of encapsulated enzyme was studied using peroxidase substrates. The encapsulated peroxidase enzymes showed better catalytically activity compared to free enzyme under broad range of pH conditions tested. Better catalytic activity of enzyme upon encapsulation can be attributed to high local concentration of enzyme and the unique confined environment provided by SsDPS cage. In this study, we report first example of enzyme encapsulation inside smallest known protein cage DPS. Considering DPS nanocage`s potential to cross glomerular filtration barrier, this nano-formulation has potential to deliver antioxidant cargo in kidney to mitigate oxidative stress.

Antioxidant enzyme encapsulation inside archaeal Dps nanocage

ACS Fall 2020 Virtual Meeting

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