How to restrict a store based on a responsibility

We are on Oracle ebiz R12 and have implemented iProcurement with several staores. I need to isolate one store so only people with one responsibility can use it. I have tried to create a content zone and in the 'Assign Content Zone Security' selected the responsibility that I want the store to restrict to, however, it is not working and users using the default 'Internet Procurement' responsibility can access the smart form attached to the store.

Any suggestions??

Thanks

NAushad