Peptitergent PD1 affects the GTPase activity of rat brain cortical membranes

Peptitergent PD1 shows complex effects on GTPase activity of rat brain cortical membranes: inhibition in the presence of lower concentrations of GTP and activation at a higher concentration, above 0.5 mu M, of GTP. Its effect is dose dependent and is characterized by an EC50 of 1.8 +/- 0.2 mu M and a Hill coefficient of 1.6 +/- 0.3, and it increases both K-m and V-max of the GTP hydrolysis, PD1 that was unable to solubilize G-proteins from the membranes probably acts on them by direct binding near the C-terminal alpha-helical region of the G(alpha) subunit, similarly to mastoparan. (C) 1999 Elsevier Science Inc. All rights reserved.