Photoinduced Nucleic Acid-Protein Crosslinkage in Ribosomes and Ribosome Complexes

Abstract

Exposure of aqueous buffered solutions of E. coli 30S and 50S ribosomal subunits and of E. coli 70S ribosomes to ultraviolet radiation results in changes in a number of the initial physical properties of the ribosome components consistent with the formation of covalent crosslinks between the rRNA and protein components of the ribosomal subunits. These changes in physical properties include a dose-dependent decrease in the separability of the rRNA and protein components of the ribosome subunits under conditions normally denaturing for the ribosome structure, co-elution from gel filtration media of the rRNA and protein components of irradiated ribosomes under conditions where the native structure of the ribosomes is completely disrupted, enhanced mobilities of specific ribosomal proteins towards the anodic (+) electrodes in an applied electrical field, and radioactive labelling of specific ribosomal proteins in irradiated ribosomal subunits and 70S ribosomes initially labelled with tritium only in their rRNA components. Irradiation of 70S poly(x) complexes with 254 nm radiation effects changes in the separabilities of the poly(x) and 30S ribosome components of the complex, and irradiation of 70S 3H —poly(x) complexes results in the radioactive labelling of a small number of ribosomal proteins in the 30S subunit. It has therefore been concluded that covalent crosslinks are also formed between the poly(x) components of 70S poly(x) complexes and 30S ribosomal proteins. Application of the photoinduced formation of covalent crosslinks between the nucleic acid and protein components of the above ribosome systems has resulted in the identification of the mRNA-binding proteins on the 30S ribosomal subunit and determination of the relative proximities of the ribosomal proteins to the rRNA bases in the intact E. coli 30S and 50S ribosomal subunits. In addition, a molecular basis has been developed for relating the reactivity of specific ribosomal proteins in photoinduced cross-linkage to the rRNA components in their corresponding subunits to rRNA-protein interactions in the native topographical states of the ribosomal subunits.KeywordsRibosomal ProteinRibosomal SubunitCovalent CrosslinksrRNA MoleculeRibosome ComplexThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.