Proximity of 5.8 S RNA-binding proteins and A-site proteins in yeast ribosomes inferred from cross-linking.

In order to probe the spatial arrangement of proteins within the 5.8 S rRNA domain of the intact ribosomal subunit of Saccharomyces cerevisiae, 60 S ribosomal subunits were treated with 2-iminothiolane. Proteins were extracted from the cross-linked ribosomes, fractionated by Sephadex G-150 column chromatography, and analyzed by diagonal polyacrylamide-sodium dodecyl sulfate gel electrophoresis. Constituent proteins of cross-linked pairs were identified by two-dimensional polyacrylamide gel electrophoresis. Nine cross-links involving five of the 11 5.8 S rRNA-binding proteins were analyzed. A model showing the network of cross-links is presented. Several of the 5.8 S rRNA-binding proteins are in sufficiently close proximity of the ribosomal A-site proteins to be cross-linked.