Emacs is not written using the Xt library by default, so there are no “translations” to be set. (We aren't sure how to set such translations if you do build Emacs with Xt; please let us know if you've done this!)
The only way to affect the behavior of keys within Emacs is through
xmodmap (outside Emacs) or
define-key (inside Emacs). The
define-key command should be used in conjunction with the
function-key-map map. For instance,
(define-key function-key-map [M-<TAB>] [?\M-\t])
defines the M-<TAB> key sequence.