The Mdmx oncoprotein has only recently emerged as a critical-independent to
Mdm2-regulator of p53 activation. We have determined the crystal structure of
the N-terminal domain of human Mdmx bound to a 15-residue transactivation domain
peptide of human p53. The structure shows why antagonists of the Mdm2 binding to
p53 are ineffective in the Mdmx-p53 interaction.