Structural fingerprints of the Ras-GTPase activating proteins neurofibromin and p120GAP.
Ras specific GTPase activating proteins (GAPs), neurofibromin and p120GAP, bind GTP bound Ras and efficiently complement its active site. Here we present comparative data from mutations and fluorescence-based assays of the catalytic domains of both RasGAPs and interpret them using the crystal structures. Three prominent regions in RasGAPs, the arginine-finger loop, the phenylalanine-leucine-arginine (FLR) region and alpha7/variable loop contain structural fingerprints governing the GAP function. The finger loop is crucial for the stabilization of the transition state of the GTPase reaction. This function is controlled by residues proximal to the catalytic arginine, which are strikingly different between the two RasGAPs. These residues specifically determine the orientation and therefore the positioning of the arginine finger in the Ras active site. The invariant FLR region, a hallmark for RasGAPs, indirectly contributes to GTPase stimulation by forming a scaffold, which stabilizes Ras switch regions. We show that a long hydrophobic side-chain in the FLR region is crucial for this function. The alpha7/variable loop uses several conserved residues including two lysine residues, which are involved in numerous interactions with the switch I region of Ras. This region determines the specificity of the Ras-RasGAP interaction.
Ahmadian
Mohammad Reza
MR
Department Structural Biology, Max-Planck-Institute for Molecular Physiology, Otto-Hahn-Strasse 11, 44227, Dortmund, Germany.
Kiel
Christina
C
Stege
Patricia
P
Scheffzek
Klaus
K
D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003878:Dermatoglyphics; D006801:Humans; D007700:Kinetics; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D025542:Neurofibromin 1 / Q000737:chemistry* / Q000378:metabolism*; D010649:Phenylalanine / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020729:p120 GTPase Activating Protein / Q000737:chemistry* / Q000378:metabolism*
D025542:Neurofibromin 1; D011994:Recombinant Proteins; D020729:p120 GTPase Activating Protein; D010649:Phenylalanine; D001120:Arginine; D007930:Leucine