Carboxyl methylation of the low molecular weight GTP-binding protein G25K: regulation of carboxyl methylation by rhoGDI.

ABSTRACT

A soluble form of G25K from brain co-purified with a 28 kDa protein, which was identified as guanine nucleotide dissociation inhibitor (GDI) protein, similar or identical to rhoGDI. The GDI protein inhibited the dissociation of GDP from G25K. G25K and the GDI protein form a heterodimer and remain associated with either GDP or GTP gamma S bound. The GDI protein inhibited carboxyl methylation of G25K in the presence of magnesium and GDP. The GDI protein appears to be an important regulator of G25K methylation by blocking methylation of G25K in the inactive GDP-bound conformation.