Preliminary crystallographic analysis of the antibiotic discharge outer membrane lipoprotein OprM of Pseudomonas aeruginosa with an exceptionally long unit cell and complex lattice structure

Crystals of the drug-discharge outer membrane protein OprM (MW = 50.9 kDa) of the MexAB-OprM multidrug transporter of Pseudomonas aeruginosa have been grown at 293 K in the presence of 2-methyl-2,4-propanediol and a combination of surfactants. The crystal belonged to space group R32, with unit-cell parameters a = b = 85.43, c = 1044.3 angstrom. Diffraction data for OprM were obtained using the undulator synchrotron-radiation beamline at SPring-8 (BL44XU, Osaka University), which allowed an extra-long specimen-to-detector distance with a wide detector area. The crystal diffracted to 2.56 angstrom resolution using 0.9 angstrom X-rays from the synchrotron-radiation source. A heavy-atom derivative for isomorphous replacement phasing was obtained using iridium chloride.