Deactivate *all* gnome shortcuts for alt-shift-right?

I'm using Gnome Shell 3.4.1. I also use org-mode in Emacs. One of the very commonly-used key bindings in org is alt-shift-right arrow, which demotes an outline heading and all of its contents.

Gnome Shell is not passing this key sequence into Emacs at all. That is, I press the keys and nothing happens.

I looked in the keyboard shortcuts control panel, and at present, it doesn't show anything bound to that key sequence. (It's been a while since I set it up, so I don't remember if this key sequence is bound to something by default. If it is, then I removed that binding along time ago, but it doesn't help the situation.)

How do I tell Gnome Shell to stop swallowing this key sequence?

hjh