Expression, purification, crystallization and preliminary X-ray analysis of Pseudomonas aeruginosa AlgX

AlgX is a periplasmic protein required for the production of the exopoly­saccharide alginate in Pseudomonas sp. and Azotobacter vinelandii. AlgX has been overexpressed and purified and diffraction-quality crystals have been grown using iterative seeding and the hanging-drop vapor-diffusion method. The crystals grew as flat plates with unit-cell parameters a = 46.4, b = 120.6, c = 86.9 Å, β = 95.7°. The crystals exhibited the symmetry of space group P2₁ and diffracted to a minimum d-spacing of 2.1 Å. On the basis of the Matthews coefficient (V_M = 2.25 ų Da⁻¹), two molecules were estimated to be present in the asymmetric unit.