PTRX was chosen as a simple, easy to implement, and easy to audit solution to collect and manage a pool of assets.
The primary purpose of the pool is to act as the recapitalization resource for USDJ. If a CDP gets liquidated without enough collateral to cover the debt, additional funds are drawn from the pool to cover the difference. As a result, all PTRX holders have their proportional TRX claims diluted to make up for the shortfall.
This is how ‘risk’ is transferred away from USDJ holders in the broader crypto ecosystem, and towards CDP owners specifically. This risk being that PTRX holdings could be negatively affected by a sudden, steep crash in the market price of TRX, or if the value of the collateral continues to fall as it is being sold.
The system can reward PTRX holders as well. Through the application of penalties to users who allow their CDPs to become liquidated, fees applied to people buying and selling PTRX shares, and through surpluses from excess collateral sales.
This pool of assets is also the source of funds that are inflated in the event of an Emergency Shutdown.