Defend with A5 in the BB?

[pokerhooker]

100/200 blinds, I'm in the BB with A[img]/images/graemlins/heart.gif[/img]5[img]/images/graemlins/heart.gif[/img]. MP open raises for 400 (2xBB), folded to me in the BB, i have 3700 and he has me covered with ~4500. At this point, the pot is definitely laying me odds to call (damn mini raisers), but the problem is if I flop my A, if I am in fact dominated by a better A, I'm now out of position and ready to take a huge fall. Would you guys defend in this spot?

True to form, the flop came A[img]/images/graemlins/spade.gif[/img]T[img]/images/graemlins/heart.gif[/img]4[img]/images/graemlins/club.gif[/img]. Now what is your play? I led out and bet half the pot, planning to fold to a substantial re-raise.

He just called, which made me skeptical he had an A, and now I'm hating my smallish bet on the flop. Turn is ( A[img]/images/graemlins/spade.gif[/img]T[img]/images/graemlins/heart.gif[/img]4[img]/images/graemlins/club.gif[/img])Q[img]/images/graemlins/heart.gif[/img], a card which as soon as it hit I knew I didnt like, but with his weak call on the flop and my increased outs for a flush draw, I decided to push my remaining 3000 into a pot of 2000. What's your take on this?

Of course, he calls and shows KJ for the gutshot straight [img]/images/graemlins/tongue.gif[/img]