The Rnd proteins constitute an exceptional subfamily within the Rho GTPase family. They possess extended chains at both termini and four prominent amino acid deviations causing GTPase deficiency. Herein, we report the crystal structure of the Rnd3/RhoE G-domain (amino acids 19–200) at 2.0 Å resolution. This is the first GTP-structure of a Rho family member which reveals a similar fold but striking differences from RhoA concerning (i) GTPase center, (ii) charge distribution at several surface areas, (iii) C3-transferase binding site and (iv) interacting interfaces towards RhoA regulators and effectors.
