ROLE OF BOUND GDP IN THE STABILITY OF THE RHO A-RHO GDI COMPLEX PURIFIED FROM NEUTROPHIL CYTOSOL

The rho A-rho GDI complex purified from bovine neutrophil cytosol was found to contain GDP as the only bound nucleotide at a ratio of 1 mol of GDP per mol of complex. The rho GDI component of the complex (pi 4.8-5.0, apparent molecular mass 28-29 kDa) and the rho A component (pi scattered between 5.0-6.2, apparent molecular mass 24 kDa) were resolved by 2D gel electrophoresis. Upon dephosphorylation of bound GDP by apyrase, the rho A component of the complex was prone to proteolytic cleavage. The integrity of rho A in the presence of apyrase was preserved by addition of excess GTP. These data suggest that rho A liganded by GDP in the rho A-rho GDI complex is maintained in a conformation that escapes action of proteases. (C) 1994 Academic Press, Inc.