The N-terminal domain of the Caulobacter crescentus CgtA protein does not function as a guanine nucleotide exchange factor (vol 484, pg 29, 2000)

The Caulobacter crescentus GTP binding protein CgtA is a member of the Obg/ GTP1 subfamily of monomeric GTP binding proteins. In vitro, CgtA displays m oderate affinity for both GDP and GTP, and rapid exchange rate constants fo r either nucleotide. One possible explanation for the observed rapid guanin e nucleotide exchange rates is that CgtA is a bimodal protein with a C-term inal GTP binding domain and an N-terminal guanine nucleotide exchange facto r (GEF) domain. In this study we demonstrate that although the N-terminus o f CgtA is required for function in vivo, this domain plays no significant r ole in the guanine nucleotide binding, exchange or GTPase activity. (C) 200 1 Federation of European Biochemical Societies. Published by Elsevier Scien ce B.V. All rights reserved.