SdsA polymorphs isolation and improvement of their crystal quality using non-conventional crystallisation techniques

AbstractWe crystallised SdsA, a sodium dodecyl sulphate hydrolase, from Pseudomonas aeruginosa in three different crystal polymorphs and determined their three-dimensional structure. The different polymorphs present different crystal packing habits. One of the polymorphs suggests the existence of a tetramer, an oligomeric state not observed previously, while the crystal packing of the remaining two polymorphs obstructs the active site entrance but stabilizes flexible regions of the protein. Non-conventional crystallisation methods that minimise convection such as counter-diffusion in polyvinyl alcohol gel coupled with the influence of a 500 MHz (10.2 Tesla) magnetic field were necessary to isolate the poorest diffracting polymorph and increase its internal order to determine its structure by X-ray diffraction. Our results show the effectiveness of non-conventional crystallographic methods to isolate different crystal polymorphs.