“A Sample Can Tell a Story when Pressed by Classification: Three coexisting States of the Pre-translocational Ribosome”
Joachim Frank, Ph.D. – Howard Hughes Medical Institute Investigator, Professor Department of Biochemistry and Molecular Biophysics, and Department of Biology, Columbia University New York
dataset of 250,000 particles of the pre-translocational ribosome prepared in the absence of EF-G and at 3.5 mM Mg++ was analyzed with the Maximum Likelihood reconstruction program ML3D. In addition to the two highly populated states previously reported (classical tRNA positions A/A, P/P; ribosome unratcheted versus hybrid tRNA positions A/P, P/E; ribosome ratcheted), we now see a highly populated intermediate state.
Thus, in the absence of a factor, the pretranslocational ribosome fluctuates between at least three states, each exhibiting a distinct conformation of the ribosome and configuration of tRNA binding.