Cloning, purification, crystallization and preliminary X-ray analysis of a bacterial GABA receptor with a Venus flytrap fold.

In response to infection by the pathogen Agrobacterium tumefaciens, plants synthesize several stress amino acids, including gamma-aminobutyric acid (GABA), which modulates the expression of bacterial virulence factors. GABA penetrates into the bacterial cytoplasm via an ABC transporter that is associated with the periplasmic receptor Atu2422. Mature receptor Atu2422 (without its signal peptide) was overexpressed in Escherichia coli, purified and crystallized. A complete data set was collected to 1.35 A resolution at 100 K. The crystals belonged to the monoclinic space group C2 and contained one molecule in the asymmetric unit. Molecular replacement was performed and the initial electron-density maps revealed a closed form of this Venus flytrap (VFT) receptor, suggesting the presence of an endogenous E. coli ligand.