Physical studies on a nucleoprotein from the ribosome of E. coli.

Bacterial 5S RNA and its cognate proteins constitute an attractive system to study nucleoprotein interactions. The molecular weights of the components involved are modest and they can be prepared in the quantities necessary to permit the application of material-intensive techniques like NMR and X-ray crystallography. 5S RNA is being examined by proton NMR at 500 MHz with special attention paid to the downfield NH proton region. A substantial number of assignments can be suggested in this region based on nuclear Overhauser results. The binding of protein L25 (E. coli) to the RNA gives rise to a highly characteristic set of perturbations in the spectrum of the RNA. The data suggest a localized and assignable alteration in RNA structure upon formation of the complex. In addition we have grown large crystals of RNAs related to 5S RNA and their complexes with a cognate protein. The properties of these crystals and the progress made in analyzing their structure are discussed.