Crystallization and preliminary X-ray crystallographic analysis of ribosome assembly factors: the Rpf2-Rrs1 complex.

Rpf2 and Rrs1 are essential proteins for ribosome biogenesis. These proteins form a complex (the Rpf2-subcomplex) with 5S rRNA and two ribosomal proteins (L5 and L11). This complex is recruited to the ribosome precursor (the 90S pre-ribosome). This recruitment is necessary for the maturation of 25S rRNA. Genetic depletion of Rpf2 and Rrs1 results in accumulation of the 25S rRNA precursor. In this study, Rpf2 and Rrs1 from Aspergillus nidulans were co-overexpressed in Escherichia coli, purified and crystallized. Subsequent analysis revealed that these crystals contained the central core region of the complex consisting of both N-terminal domains. X-ray diffraction data were collected to 2.35 Å resolution. Preliminary analysis revealed that the crystals belonged to space group P212121, with unit-cell parameters a = 54.1, b = 123.3, c = 133.8 Å. There are two complexes in the asymmetric unit. Structure determination using selenomethionine-labelled protein is in progress.