Cloning, expression, crystallization and preliminary X-ray crystallographic analysis of the co-chaperonin XoGroES from Xanthomonas oryzae pv. oryzae

Bacterial blight (BB), a devastating disease caused by Xanthomonas oryzae pv. oryzae (Xoo), causes serious production losses of rice in Asian countries. Protein misfolding may interfere with the function of proteins in all living cells and must be prevented to avoid cellular disaster. All cells naturally contain molecular chaperones that assist the unfolded proteins in folding into the native structure. One of the well characterized chaperone complexes is GroEL-GroES. GroEL, which consists of two chambers, captures misfolded proteins and refolds them. GroES is a co-chaperonin protein that assists the GroEL protein as a lid that temporarily closes the chamber during the folding process. Xoo4289, the GroES gene from Xoo, was cloned and expressed for X-ray crystallographic study. The purified protein (XoGroES) was crystallized using the hanging-drop vapour-diffusion method and a crystal diffracted to 2.0 Å resolution. The crystal belonged to the hexagonal space group P6₁, with unit-cell parameters a = 64.4, c = 36.5 Å. The crystal contains a single molecule in the asymmetric unit, with a corresponding V_M of 2.05 Å³ Da^-1 and a solvent content of 39.9%.