25nl; straight on A high river.

[Schiester]

$0.10/$0.25 Blinds - 6 Players - (LegoPoker Hand History Converter)

Villan is 24/4/.6 (107)

SB: $2.29
BB: $25.63
UTG: $27.43
Hero (MP): $23.66
CO: $27.08
BTN: $27.15

Preflop: Hero is dealt K[img]/images/graemlins/diamond.gif[/img] J[img]/images/graemlins/diamond.gif[/img] (6 Players)
UTG calls $0.25, <font color="red">Hero raises to $1.25</font>, 4 folds, UTG calls $1.00

Flop: ($2.85) Q[img]/images/graemlins/heart.gif[/img] K[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/heart.gif[/img] (2 Players)
UTG checks, <font color="red">Hero bets $2.25</font>, UTG calls $2.25

Turn: ($7.35) T[img]/images/graemlins/heart.gif[/img] (2 Players)
UTG checks, Hero checks

River: ($7.35) A[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">UTG bets $5.00</font>, Hero ?????


I checked turn expecting villan to have made flush.

River card makes much of villans range look appealing enough to him to bet river.

How much should I be calling on this board?