Dithiothreitol (DTT) and ampicillin (AMP) were purchased from GoldBio. Restriction enzymes and primers were purchased from Integrated DNA Technologies. Protease-inhibitor tablets were purchased from Sigma-Aldrich. All other buffers and reagents were purchased from Sigma-Aldrich or Fisher. The substrate p-nitrophenyl phosphate (pNPP) was synthesized using published methods. Crystallography screens, trays, and coverslips were purchased from Hampton Research.