Whenever I've seen pictures of the SS in orbit, it is with its roof facing towards the earth. I don't know if that's the cause or effect of the turn.
Just off the top of my head the Thrust: Drag couple, if similar to a conventinal a/c, would indicate a pitch up moment, so perhaps the turn is to compensate for this.
[This message has been edited by A Very Civil Pilot (edited 08 December 2000).]