We currently offer two fluorescent assay formats that are suitable for measuring the activity of both Ras and Rho family GEFs. These assays measure different steps in the GEF reaction (Fig. 1), which allows them to be leveraged in unique ways. Our original assay offering utilizes mant-GTP to monitor the binding of GTP to a small G-protein in the exchange reaction, and the format of this assay allows for an inhibitor/activator (e.g. small molecule, peptide, protein, etc.) to be pre-incubated with the small G-protein prior to the addition of the GEF. The mant-GTP exchange assay is the foundation of our Rho GEF Exchange Assay Kit (Cat# BK100), which includes hDbs (RhoGEF), RhoA, Rac1, and Cdc42 proteins.

Our latest GEF assay offering monitors the release of GDP during the exchange reaction and utilizes Bodipy-FL-GDP that is pre-bound to the small G-protein of interest. In this assay format, it is possible to pre-incubate an inhibitor/activator with a GEF of interest prior to the addition of the small G-protein:Bodipy-FL-GDP complex. Thus, depending on the nature of your inhibitor design you have the option of a pre-incubation step with either the GEF or small G-protein. Both assay formats work well with our existing (i.e. hDbs) and new Rho and Ras family GEFs (i.e. Vav1, Vav2, Tiam1, and RasGRF1).

Figure 1. The basic elements of the mant-GTP exchange assay that monitors GTP binding to a small G-protein in the exchange reaction (A). Representative data using Sos1 and K-Ras4B in the mant-GTP exchange assay (B). Elements of the Bodipy-FL-GDP exchange assay that monitors GDP release during the exchange reaction (C). Representative data using Sos1 and K-Ras4B in the Bodipy-FL-GDP exchange assay (D).

Currently available GTP Exchange Factor Screens

SOS1 GEF protein (Exchange domain, aa 564-1049) protein                           CS-GE02

RasGRF1 GEF Protein (Cdc25 Exchange Domain, aa 1038-1270)                    CS-GE03

Tiam1 GEF Protein (DHPH Exchange Domain, aa 1040-1406)                         CS-GE04

Vav1 GEF Protein (DHPHC1 Exchange Domain, Y174D mutant, aa 168-522) CS-GE05

Vav2 GEF Protein (DH Exchange Domain, aa 189-374)                                    CS-GE06

ARNO GEF Protein (Exchange domain)                                                             CS-GE07

SOS2 GEF Protein (Exchange domain)                                                              CS-GE08

RapGEF5 Exchange domain                                                                                CS-GE09

H-Ras His-tagged full length human protein                                     RS01

K-Ras4B His-tagged full length human protein                                CS-RS03

K-Ras4B G12V Mutant His-tagged full length human protein         CS-RS04

K-Ras4B G13D Mutant His-tagged full length human protein         CS-RS06

K-Ras4B G13S Mutant His-tagged full length human protein         CS-RS07

K-Ras4B K128A Mutant His-tagged full length human protein       CS-RS08

K-Ras4B Q61P Mutant His-tagged full length human protein         CS-RS09

K-Ras4B R135A Mutant His-tagged full length human protein       CS-RS10

K-Ras4B G12D+I36N Mutant His-tagged full length human protein, drug binding site tool      CS-RS11

K-Ras4B G12D+D38A Mutant His-tagged full length human protein, drug binding site tool     CS-RS12

K-Ras4B G12D Mutant His-tagged full length human protein        CS-RS13

K-Ras4B G12C Mutant His-tagged full length human protein        CS-RS14

N-Ras His-tagged full length human                                                 CS-RS02

R-Ras His-tagged full length human                                                 CS-RS05

RhoA His-tagged full length human                                                 RH01RhoA protein: His tagged: human constitutively active                R6301RhoA protein: GST tagged: human wild type                                 RHG01

Rac2 His-tagged full length human                                                  RC02Rac1 protein: His tagged: human constitutively active                 R6101Rac1 protein: GST tagged: human dominant negative                  R17G01Rac1 protein: GST tagged: human wild type                                  RCG01Cdc42 protein: GST tagged: human wild type                                CDG01Cdc42 protein: His tagged: human wild type                                  CD01Cdc42 protein: His tagged: human constitutively active               C6101

Dbs Target (DHPH domain, aa 623-967, human, 6xHis-tagged)                CDS100RasGRF1 Target (Cdc25 domain, aa 1038-1270, human, MBP fusion)     CDS102SOS1 Target (REM-Cdc25 domain, aa 564-1049, human, 6xHis-tagged)  CDS103SOS2 Target (REM-Cdc25 domain, human, 6xHis tagged)                        CDS117

RapGEF5 Target (Exchange domain plus Rap1B protein)                        CDS118