Best bet would be to go to a real paint store and get the paint. Having made that point, paint and primer is nothing more than a marketing scheme, go ahead and use it, no harm will be done, it is just paint, there is no primer in the can.

Here is more info

Here is a link that might be useful: paint and primer

People (generally DIYers) have always taken shortcuts and tried to skip priming. Paint and primer in one is a marketing gimmick, yes, started by depot and picked up by others (including Ace, Valspar, and Benjamin Moore) because customers started demanding it. A paint that claims to be self-priming should seal and adhere on it's own (without primer) better than a non-self-primimg paint would do. In other words, they figured out people skip priming and designed the paint better so they can get away with it better. However, priming is still a good step (crucial in some instances), so just think of paint-and-primer-in-one as being the upper end paint from that store. We may not all be fans of Behr, but you're using the best top-coat Behr had to offer to cover your primer.

And gosh I hope that makes sense...I feel like I'm talking in circles, but it's the best I can do tonight!