Ac domestic flights operate out of Terminal 2.
Ac international flights operate out of new Terminal 1.
There is a bus transfer between teminals about every 10 minutes (free).
An hour sounds a bit tight. If you have to collect your bags off the domestic flight, then it is too tight.
http://www.gtaa.com/Index.aspx?Sid=Node2/Node2.2&Tpl=1