Figure 2. Nop53p physically interacts with rRNA processing factors involved in pre-60 S ribosomal subunit biogenesis.

Nop53p was immunopurified from a nuclear fraction prepared from cells expressing an Nop53p–pA chimaera. Proteins bound to Nop53p–pA were eluted with MgCl₂ at increasing concentrations and analysed by SDS/PAGE followed by Coomassie Blue staining. The MgCl₂ concentrations are noted above each lane. Molecular mass standards are shown at the left. Proteins corresponding to the numbered bands were identified by tandem MS of excised gel slices. Bands 1–6 were identified as Nop53p, Nop2p, Cbf5p, Fpr3p, Fpr4p and ribosomal proteins, respectively. Proteins that migrated below the 31 kDa marker were excised together and contained numerous 40 and 60 S ribosomal subunit proteins.