Dynamics of the assembling ribosome

COMP 29

James R. Williamson, jrwill@scripps.edu, Department of Molecular Biology and the Skaggs Institute for Chemical Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
We are investigating the assembly of the 30S ribosomal subunit in vitro and in cells using quantitative mass spectrometry. The 30S subunit is composed of 20 small proteins that bind to the 1542 nucleotide 16S ribosomal RNA in a cascade of sequential and parallel events. Binding of each protein reports on the local RNA folding, and monitoring the kinetics of protein binding reveals the overall progression of RNA folding during 30S assembly. We have developed an isotope pulse-chase assay to monitor the binding of 20 proteins simultaneously to the 16S rRNA. Most recently, we have extended this experimental approach to include electrospray ionization and liquid chromatography coupled mass spectrometry, which provides improved sensitivity and improved accuracy of the derived rates. We have also adapted this approach to study the assembly dynamics of ribosomes in rapidly growing E. coli.