Crystallization and preliminary X-ray diffraction of the DEAD-box protein Mss116p complexed with an RNA oligonucleotide and AMP-PNP

The Saccharomyces cerevisiae DEAD-box protein Mss116p is a general RNA chaperone which functions in mitochondrial group I and group II intron splicing, translation and RNA-end processing. For crystallization trials, full-length Mss116p and a C-terminally truncated protein (Mss116p/Delta 598-664) were overproduced in Escherichia coli and purified to homogeneity. Mss116p exhibited low solubility in standard solutions (<= 1 mg ml(-1)), but its solubility could be increased by adding 50 mM l-arginine plus 50 mM l-glutamate and 50% glycerol to achieve concentrations of similar to 10 mg ml(-1). Initial crystals were obtained by the microbatch method in the presence of a U-10 RNA oligonucleotide and the ATP analog AMP-PNP and were then improved by using seeding and sitting-drop vapor diffusion. A cryocooled crystal of Mss116p/Delta 598-664 in complex with AMP-PNP and U10 belonged to space group P2(1)2(1)2, with unit-cell parameters a = 88.54, b = 126.52, c = 55.52 angstrom, and diffracted X-rays to beyond 1.9 angstrom resolution using synchrotron radiation from sector 21 at the Advanced Photon Source.