Transcreener GDP assay directly measures GDP produced by GTPases when GEF proteins stimulate the enzyme. These GDP measurements allow researchers to effectively determine the GEF activity. The assay provides a powerful tool to screen compound libraries for GEF modulators to help find new therapies for disease.

Active Rho GTPases stimulate cell growth and migration, sometimes triggering tumorigenesis or invasion. Rho GEFs (guanine nucleotide exchange factors) positively regulate Rho GTPases by accelerating GDP dissociation and allowing the formation of the active GTPase-GTP complex.

By accelerating GDP dissociation, the rate-limiting step of the GTPase catalytic cycle, GEFs enhance the steady state rates of GTP hydrolysis by GTPases. These changes can be detected using the Transcreener® GDP GEF Assay, which relies on a highly selective antibody and far-red fluorescent tracer to allow homogeneous detection of GDP with fluorescence readouts.