A new crystal form of large ribosomal subunits from Halobacterium marismortui

A new form of three-dimensional crystals of the 50 S ribosomal subunits from Halobacterium marismortui has been obtained at 19°C, using polyethylene glycol in the presence of 1.2–1.7 M KCl in the crystallization mixture. The crystals diffract X-rays to 13 A and are stable in the synchrotron radiation beam for 4–8 h. Being aggregates of thin plates, the dimensions of only two unit cell edges, 147 × 181 A, with an angle of 95°, could so far be determined by both X-ray crystallography and electron microscopy. Attempts to produce thicker crystals by sophisticated seeding are in progress.