Measurement of the GTPase Activity of Signal-Transducing G-Proteins in Neuronal Membranes

  • Marva Sweeney
Part of the Methods in Molecular Biology™ book series (MIMB, volume 41)


The methods described in this chapter are designed to measure the hydrolysis of guanosine triphosphate (GTP) to inorganic phosphate (Pi) and guanosine diphosphate (GDP), a reaction catalyzed by the GTPase enzymes (EC 3.6.1.-). The theory behind the experimental design involves using [γ-32P]GTP as a marker, whereby any GTPase-induced hydrolysis will result in the 32P label appearing as 32P, and as unhydrolyzed [γ-32P]GTP. It was originally described by Cassel and Selinger (1). 32P, must be separated from [γ-32P]GTP, and then can be easily quantitated by using a liquid scintillation counter. The amount of 32Pi is directly proportional to the amount of [γ-32P]GTP hydrolyzed, and, therefore, proportional to the activity of GTPases in the preparation.


GTPase Activity Guanosine Triphosphate Guanosine Diphosphate Trypsin Inhibitor Unit Nonhydrolyzable Analog 
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Copyright information

© Humana Press Inc , Totowa, NJ 1995

Authors and Affiliations

  • Marva Sweeney
    • 1
  1. 1.Department of Physiology, College of MedicineUniversity of SaskatchewanSaskatoonCanada

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