The Colnago rider beat Australians Matt Goss (GreenEdge) and stage four winner Mark Renshaw (Rabobank) to the line at the end of the 148km trek from Bodrum.
It was a fourth second place finish for Goss in this year's race as Colnago-CSF Inox recorded their second consecutive stage win.
Stage three winner Ivailo Gabrovski (Konya Seker) retained his 1:33 lead on GC with two stages to go.
Frederik Veuchelen, Maksim Belkov, ninth overall, and Ireland's Philip Deignan broke out of an initial 20-man escape to form a 4:30 lead over the peloton in the race's longest stage.
An attempt by a group including, amongst others, England's Andrew Fenn and stage two winner Andre Greipel was foiled before the lead trio were caught with 8km remaining.
A counter-attack by Enrico Battaglin was neutralised by 500m remaining but his team-mate Modolo was on hand to claim his first victory of the season.