Optimal Affinity Enhancement by a Conserved Flexible Linker Controls p53 Mimicry in MdmX

BORCHERDS, WADE; BECKER ANDREAS; CHEN LIHONG; CHEN JIANDONG; CHEMES LUCÍA BEATRIZ; DAUGHDRILL GARY

BIOPHYSICAL JOURNAL

CELL PRESS

Lugar: United States; Año: 2017 vol. 112 p. 1 - 5

0006-3495

ABSTRACT MdmX contains an intramolecular binding motif that mimics the binding of the p53 tumor suppressor. This intramolecularbinding motif is connected to the p53 binding domain of MdmX by a conserved flexible linker that is 85 residues long.The sequence of this flexible linker has an identity of 51% based on multiple protein sequence alignments of 52 MdmX homologs.We used polymer statistics to estimate a global KD value for p53 binding to MdmX in the presence of the flexible linker andthe intramolecular binding motif by assuming the flexible linker behaves as a wormlike chain. The global KD estimated from thewormlike chain modeling was nearly identical to the value measured using isothermal titration calorimetry. According to our calculationsand measurements, the intramolecular binding motif reduces the apparent affinity of p53 for MdmX by a factor of 400.This study promotes a more quantitative understanding of the role that flexible linkers play in intramolecular binding and providesvaluable information to further studies of cellular inhibition of the p53/MdmX interaction.