The move is politically significant since Legislative Affairs has hitherto been handled by D Sridhar Babu who belongs to the Telangana region, while Sailajanath is a vocal supporter of a "united" Andhra Pradesh.
Sridhar Babu has also been given additional charge of commercial taxes.
The AP legislative assembly is expected to take up the debate on the draft Telangana Bill when its winter session resumes on January 3, 2014.
In another change, AP tourism minister Vasant Kumar has been given additional charge of Language (Promotion of Telugu).