IDENTIFICATION OF AN ESSENTIAL CAULOBACTER-CRESCENTUS GENE ENCODING AMEMBER OF THE OBG FAMILY OF GTP-BINDING PROTEINS

We have identified an essential Caulobacter crescentus gene (cgtA) tha t encodes a member of a recently identified subfamily of GTPases (the Obg family) conserved from Bacteria to Archaea to humans, This evoluti onary conservation between distantly related species suggests that thi s family of GTP-binding proteins possesses a fundamental, yet unknown, cellular role, In this report, we describe the isolation and sequence of the cgtA gene, The predicted CgtA protein displays striking simila rity to the Obg family of small, monomeric GTP-binding proteins, both in the conserved guanine nucleotide-binding domains and throughout the N-terminal glycine-rich domain that is found in many members of the O bg family. Disruption of the cgtA gene was lethal, demonstrating that this gene is essential for cell growth, Immunoblot analysis revealed t hat CgtA protein levels remained constant throughout the C. crescentus cell cycle.