The bacterial ribosome [Elektronische Ressource] : testing a new concept for translational initiation / vorgelegt von Daniela Wittek

The bacterial ribosome: Testing a new concept for translational initiation APPENDIX: Solving preparation problems for tmRNA•70S complexes Dissertation zur Erlangung des akademischen Grades des Doktors der Naturwissenschaften (Dr. rer. nat.) eingereicht im Fachbereich Biologie, Chemie, Pharmazie der Freien Universität Berlin vorgelegt von Daniela Wittek aus Berlin 2009 1 Disputation: 17.12.2009 Gutachter: 1. Prof. Dr. Rupert Mutzel 2. Prof. Dr. Knud H. Nierhaus Summary Protein synthesis encompasses three universal steps initiation, elongation and termination. The standard model for initiation is that the small 30S subunit finds the initiation signals on an mRNA with the help of three monomeric factors IF1, IF2 and IF3. IF1 and IF3 are believed to bind exclusively to the 30S subunit rather than to 70S ribosomes. This 30S-binding mode as standard initiation type cannot easily be reconciled with a number of observations. We developed a hypothesis according to which these inconsistencies are resolved, namely the 70S-scanning mode saying that a 70S does not dissociate after the translation of a cistron, but is able to scan in both directions on the mRNA checking for another initiation signal of a downstream cistron. In this thesis we present in vitro evidence that support this hypothesis: 1.