AKs HU but UI: Call it down?

[TomBrooks]

Pacific $1/$2 6M/5Hands LH'em

No read

PREFLOP: TomBrooks is small blind with K[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/club.gif[/img]
UTG calls, fold, Button calls, TB raises, fold, call, call.

FLOP: (7SB)6[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/spade.gif[/img].
TomBrooks checks, check, Button bets, call, fold.

TURN: (4.5BB) 5[img]/images/graemlins/diamond.gif[/img]
TomBrook checks, Button bets, call.

RIVER: (6.5BB) Q[img]/images/graemlins/club.gif[/img]
TB checks, Button bets, TB calls.

Call the flop? No straight or flush chances, but it's heads up. Call the turn? Call the river?