Ribonucleic acid-protein cross-linking in Escherichia coli ribosomes: (4-azidophenyl)glyoxal, a novel heterobifunctional reagent.

Abstract

We have used the heterobifunctional reagent (4-azidophenyl)glyoxal (APG) to cross-link RNA to protein in Escherichia coli 30S ribosomal subunits. Synthesis and characterization of the reagent are described. Like other dicarbonyl reagents (e.g., kethoxal), APG reacts specifically with guanosine among the four ribonucleosides. The azido group in APG can be photolyzed with UV light (lambda greater than 300 nm), yielding an unstable nitrene which is potentially reactive with many groups in proteins and nucleic acids. Conditions for APG modification of guanylic acid residues in 30S subunits are described; photolysis of bound APG results in cross-linking of approximately 5% of the total 30S proteins to 16S RNA. A specific subset of the 30S proteins is cross-linked to 16S RNA by APG.