NL25 AK 3-bet Pot Facing a Lead

[Suaimhnea]

No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

CO ($23.25)
Hero ($45.75)
SB ($25)
BB ($12.65)
UTG ($71.10)
MP ($11.55)

Preflop: Hero is Button with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 fold</font>, <font color="#CC3333">MP raises to $1</font>, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $3.25</font>, <font color="#666666">2 folds</font>, MP calls $2.25.

Flop: ($6.85) 2[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP bets $5</font>, <font color="#CC3333">Hero ???</font>

Player is relatively unknown, had seen him lead with some weaker aces in spots against loose-passive players, but not against me.

Thoughts here?