title: The crystal structure of the RhoA-AKAP-Lbc DH-PH domain complex.
abstract: The RhoGEF (Rho GTPase guanine-nucleotide-exchange factor) domain of AKAP-Lbc (A-kinase-anchoring protein-Lbc, also known as AKAP13) catalyses nucleotide exchange on RhoA and is involved in the 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 (Dbl-homologous)-PH (pleckstrin homology)] domain to 2.1 Å (1 Å = 0.1 nm) resolution. The structure reveals important differences compared with related RhoGEF proteins such as leukaemia-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 with 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 GEF inhibitors.
authors.affiliation: *Structural Genomics Consortium, Oxford University, Old Road Campus Research Building, Old Road Campus, Roosevelt Drive, Oxford OX3 7DQ, U.K.
authors.forename: Kamal R
authors.initials: KR
authors.lastname: Abdul Azeez
authors.forename: Stefan
authors.initials: S
authors.lastname: Knapp
authors.affiliation: ‡Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
authors.forename: João M P
authors.initials: JM
authors.lastname: Fernandes
authors.affiliation: ‡Max Delbrück Center for Molecular Medicine (MDC), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
authors.forename: Enno
authors.initials: E
authors.lastname: Klussmann
authors.affiliation: *Structural Genomics Consortium, Oxford University, Old Road Campus Research Building, Old Road Campus, Roosevelt Drive, Oxford OX3 7DQ, U.K.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Elkins
mesh_terms: D054758:A Kinase Anchor Proteins / Q000737:chemistry*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D020558:GTP Phosphohydrolases / Q000737:chemistry; D006801:Humans; D015778:Minor Histocompatibility Antigens; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry*; D064067:Rho Guanine Nucleotide Exchange Factors / Q000737:chemistry; D020742:rhoA GTP-Binding Protein / Q000737:chemistry*
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D015778:Minor Histocompatibility Antigens; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D020558:GTP Phosphohydrolases; D020742:rhoA GTP-Binding Protein