Crystallization and X-ray analysis of the N-terminal core domain of a tumour-associated human DEAD-box RNA helicase, rck/p54

The RCK gene was cloned on the basis of the t(11;14)(q23;q32) chromosome translocation observed in human B‐cell lymphoma cell line RC‐K8. This gene was found to be overexpressed in various kinds of tumours. The gene product, rck/p54, consisting of 472 amino‐acid residues with molecular weight 53.2 kDa, belongs to the family of DEAD‐box RNA helicases. Its ATP‐dependent RNA‐unwinding activity toward c‐myc RNA molecules in vitro has recently been demonstrated. In the present study, limited proteolysis experiments of rck/p54 were used to truncate the N‐terminal domain (residues 1–­288; 31.8 kDa) of rck/p54, leading to successful crystallization of Nc‐rck/p54, i.e. the N‐terminal core domain (residues 70–288; 24.5 kDa) of rck/p54. Crystals of Nc‐rck/p54 were grown to a size suitable for X‐ray structure analysis using polyethylene glycol 3350 as the precipitant. The crystal belongs to the orthorhombic space group P212121, with unit‐cell parameters a = 65.5, b = 73.1, c = 84.8 Å, and diffracts X‐rays to beyond 2.0 Å resolution.