Purification and crystallization of the ABC-type transport substrate-binding protein OppA from Thermoanaerobacter tengcongensis

Di- and oligopeptide- binding protein OppAs play important roles in solute and nutrient uptake, sporulation, biofilm formation, cell wall muropeptides recycling, peptide-dependent quorum-sensing responses, adherence to host cells, and a variety of other biological processes. Soluble OppA from Thermoanaerobacter tengcongensis was expressed in Escherichia coli. The protein was found to be >95% pure with SDS–PAGE after a series of purification steps and the purity was further verified by mass spectrometry. The protein was crystallized using the sitting-drop vapour-diffusion method with PEG 400 as the precipitant. Crystal diffraction extended to 2.25 Å. The crystal belonged to space group C2221, with unit-cell parameters of a = 69.395, b = 199.572, c = 131.673 Å, and α = β = γ = 90°.

► We truncated the signal peptide of OppATTE0054 to make it express in Escherichia coli as a soluble protein.
► Crystals of OppATTE0054 were grown by sitting-drop vapor diffusion method.
► The crystal of OppATTE0054 diffracted to 2.25 Å.