Flopped the nut straight, villain all-in on the river, now what?!

[Miles Ahead]

Party Poker No-Limit Hold'em, $0.50 BB (full ring, 7 players)

(There may be some errors in here -- converter didn't seem to be working right this morning.)

UTG ($105.64)
UTG+1 ($34.50)
MP ($57.05)
CO ($50.05)
Hero ($65.05)
SB ($10.65)
BB has ($57.05)

Preflop: Hero is Button with Q [img]/images/graemlins/club.gif[/img]10 [img]/images/graemlins/club.gif[/img]

SB posts a blind of $0.25. BB posts $0.50.
(UTG has been LAG pre-flop, playing more than 40% of the pots and raising often preflops (but generally smallish raises), but tight post-flop.)
UTG raises to $2.
1 fold
MP calls
(I don't have a great read on MP, except I have noticed that he will play almost any A and a lot of weak K's too and he has called down to the river with some failry weak hands (e.g., TPWK). Haven't seen much aggression from him pre- or post-flop.)
1 fold
Hero calls.
SB folds.
BB calls.

Flop: ($8.25) A[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/heart.gif[/img], J [img]/images/graemlins/club.gif[/img] (4 players)
BB checks, UTG bets $4, MP calls $4, Hero calls $4, BB folds.

Turn: ($20.25) 8[img]/images/graemlins/spade.gif[/img] (3 players)
UTG bets $4, MP calls, Hero raises to $16, UTG folds, MP calls.

The reason I raised is I had a pretty good idea based on my reads that MP has top pair, and I decided it was time to extract some more money from him (and hopefully confuse him a little). I hoped UTG would come along for the ride, and so I kept the raise close to 1/2 of what was already in the pot.

River: ($56.25) A[img]/images/graemlins/spade.gif[/img] (2 players)
MP all-in ($35.05), Hero?!