A late Luis Ricardinho penalty helped Besiktas sink Galatasaray 2-1 and leapfrog their opponents into second place in the table.
Emre Asik seemed to have salvaged a point for the visitors with his 63rd-minute effort after Besiktas had taken a 32nd-minute lead through Deivison Bobo.
But Brazilian Ricardinho made no mistake from the spot with just six minutes remaining to send Galatasaray home empty-handed.
One place below them on goal difference are Kayserispor, who beat Caykur Rizespor 1-0 despite playing the last half-hour with 10 men.
Bulent Bolukbasi saw red in the 58th minute to give hope to the struggling visitors, but Gokhan Unal popped up to grab the winner for Kayserispor 13 minutes later.
The defeat leaves Rizespor just two points above the relegation zone after Denizlispor secured a much-needed 1-0 win over Ankaragucu.
Fatih Egedik scored the only goal of the game five minutes before half-time.