James, who had already foiled Tuncay with one breathtaking save, could only parry David Wheater's injury-time header and King pounced.
England's No 1 still had work to do, blocking Afonso Alves's point-blank shot in the last action of the match to secure a valuable point in this relegation tussle.
Middlesbrough v Portsmouth: How the game unfolded
MIDDLESBROUGH NEWS FROM ACROSS THE WEB
PORTSMOUTH NEWS FROM ACROSS THE WEB
Manchester United 1-4 Liverpool
Arsenal 4-0 Blackburn
Bolton 1-3 Fulham
Everton 3-1 Stoke
Hull 1-1 Newcastle
Sunderland 1-2 Wigan
Paul Hart, Portsmouth's caretaker manager, said: 'David James is a magnificent keeper but I don't think he would thank me for singling him out, because some of theperformances of my players were immense today. We were shipping a ot of goals, something we are trying to arrest and, defensively, I thought we were tremendous.
Lifeline: Boro boss Gareth Southgate
'While we are disappointed to have conceded so late in the game, I'd probably have taken a point if you'd asked me before the game.'
It looked like being three points for a long time after Peter Crouch ended his personal goal drought by converting Glen Johnson's pass impressively for Pompey's 2,000thleague goal scored away fromFratton Park.Boro boss Gareth Southgate was unhappy with his own side's fans, who had booed several players and started chanting 'we've only got one player', in reference to Turkish striker Tuncay. He said: 'Some of the chants were disrespectful to the restof the team.'
MIDDLESBROUGH (4-4-2): Jones; McMahon, Wheater, Huth, Pogatetz (Taylor 46min); Aliadiere (A Johnson 58), Bates, Arca (Alves 71), Downing; Tuncay, King. Subs (not used): Turnbull, Emnes, Shawky, Walker. Booked: Bates. Sent off: Bates (77min).PORTSMOUTH (4-1-3-2): James; Johnson, Campbell, Distin, Hreidarsson; Davis; Pennant (Belhadj 36), Mullins, Kranjcar (Pamarot 90); Crouch, Nugent (Hughes 70). Subs (not used): Begovic, Kaboul, Utaka, Kanu. Booked: Belhadj, Nugent, Johnson.Referee: M Atkinson (W Yorkshire).
Target man: Middlesbrough's Tuncay Sanli (centre) has a shot on goal as Portsmouth's Hayden Mullins (left) and David Nugent