Structural basis for the interaction between the potato virus X resistance protein (Rx) and its cofactor ran GTPase-activating protein 2 (RanGAP2)

Abstract

The potato (Solanum tuberosum) disease resistance protein Rx has a modular arrangement that contains coiled-coil (CC), nucleotide-binding (NB), and leucine-rich repeat (LRR) domains and mediates resistance to potato virus X. The Rx N-terminal CC domain undergoes an intramolecular interaction with the Rx NB-LRR region and an intermolecular interaction with the Rx cofactor RanGAP2 (Ran GTPase-activating protein 2). Here, we report the crystal structure of the Rx CC domain in complex with the Trp-Pro-Pro (WPP) domain of RanGAP2. The structure reveals that the Rx CC domain forms a heterodimer with RanGAP2, in striking contrast to the homodimeric structure of the CC domain of the barley disease resistance protein MLA10. Structure-based mutagenesis identified residues from both the Rx CC domain and the RanGAP2 WPP domain that are crucial for their interaction and function in vitro and in vivo . Our results reveal the molecular mechanism underlying the interaction of Rx with Ran-GAP2 and identify the distinct surfaces of the Rx CC domain that are involved in intramolecular and intermolecular interactions. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.