I've just being doing some research in relation to the PAYE Tax credit and can accross this on the revenue web site:-
A Proprietary Director is the companies beneficial owner or director who controls directly/indirectly more than 15% of the company's ordinary share capital.
A point to remember, as a Proprietary Director you are not entitled to the PAYE Tax Credit.
The reference to 5% is in relation to self - Administered pension schemes, a whole different ball game.
Hope this helps !!!