X-ray crystallographic characterization and phasing of an NtrC homologue

Abstract

The ZraR (HydG) protein is a 441‐amino‐acid protein with three functional domains and is homologous to the general nitrogen‐regulatory protein NtrC that regulates nitrogen assimilation in many bacteria. The AAA and DNA‐binding domains (residues 141–441) of the ZraR protein from Salmonella typhimurium were crystallized using the sitting‐drop vapour‐diffusion method. X‐ray diffraction data from the native crystal have been collected to 3.0 Å resolution. Initial phasing was successfully performed by the SIRAS method using derivativatized crystals soaked in 1 mM ethylmercuric phosphate. Preliminary structural analysis shows the presence of a hexamer in the asymmetric unit. Model building is in progress.