The crystal structure of the RhoA-AKAP-Lbc DH-PH domain complex


  • K.R. Abdul Azeez
  • S. Knapp
  • J.M.P. Fernandes
  • E. Klussmann
  • J.M. Elkins


  • Biochemical Journal


  • Biochem J 464 (2): 231-239


  • The RhoGEF domain of AKAP-Lbc (AKAP13) catalyses nucleotide exchange on RhoA and is involved in development of cardiac hypertrophy. The RhoGEF activity of AKAP-Lbc has also been implicated in cancer. We have determined the X-ray crystal structure of the complex between RhoA:GDP and the AKAP-Lbc RhoGEF (DH-PH) domain to 2.1 {Angstrom} resolution. The structure reveals important differences compared to related RhoGEF proteins such as Leukemia-associated RhoGEF. Nucleotide exchange assays comparing the activity of the DH-PH domain to the DH domain alone showed no role for the PH domain in nucleotide exchange, which is explained by the RhoA:AKAP-Lbc structure. Comparison to a structure of the isolated AKAP-Lbc DH domain revealed a change in conformation of the N-terminal 'GEF switch' region upon binding to RhoA. Isothermal titration calorimetry showed that AKAP-Lbc has only micromolar affinity for RhoA which combined with the presence of potential binding pockets for small molecules on AKAP-Lbc raises the possibility of targeting AKAP-Lbc with guanine nucleotide exchange factor inhibitors.