Here is a little new tip/trick within the ChEMBL interface. It's possible to search by GO term - for example, if you wanted to retrieve targets (and then easily get compounds that bind to these targets) with a particular GO annotation, it's really easy to do.
So, imagine you wanted targets that were GO:0008270 (which is zinc ion binding), type this in to the search box, select the "target" search button, and you get targets retrieved that have this GO term assigned. This is really cool!
PS One issue is that the leading 0s in the GO term are significant