Cryo-EM structure of catalytic ribonucleoprotein complex RNase MRP

RNase MRP is an essential eukaryotic ribonucleoprotein complex involved in the maturation of rRNA and the regulation of the cell cycle. RNase MRP is related to the ribozyme-based RNase P, but it has evolved to have distinct cellular roles. We report a cryo-EM structure of the S. cerevisiae RNase MRP holoenzyme solved to 3.0 A. We describe the structure of this 450 kDa complex, interactions between its components, and the organization of its catalytic RNA. We show that while the catalytic center of RNase MRP is inherited from the ancestral enzyme RNase P, the substrate binding pocket of RNase MRP is significantly altered by the addition of unique RNA and protein elements, as well as by RNA-driven protein remodeling.