Following Translation and Folding of Individual Proteins by Single Ribosomes in Real-Time using Optical Tweezers

Protein synthesis is directly linked to protein folding. Translation kinetics plays a crucial role in forming secondary structural elements that lead to tertiary structure formation. However, how these two processes are coordinated is still not fully understood.Single-molecule techniques are essential for the study of protein synthesis and subsequent folding and were used in the past (1), since these are asynchronous processes that are extremely difficult to be observed using ensemble methods.Here we show for the first time to our knowledge full synthesis of three distinct proteins (hTau40, DHFR and GFPem) studied with dual-trap optical tweezers at the single-molecule level, continuing our previously published work (2). Our study explicates the intricate relationship between a protein's amino acid sequence, its co-translational elongation rate and folding.We show how hydrophobic collapse, which is the first step in protein folding, correlates with the number of hydrophobic amino acids that emerge from the ribosomal tunnel during synthesis. We also find that translational pauses are caused mainly by consecutive proline residues and positively charged amino acids. Finally, we propose a model that predicts the translation rate at a certain applied force and estimates hydrophobic collapse nucleation sites (manuscript submitted).1.Katranidis, A., D. Atta, R. Schlesinger, K. H. Nierhaus, T. Choli-Papadopoulou, I. Gregor, M. Gerrits, G. Buldt, and J. Fitter. 2009. Angew. Chem. Intl. ed 48, 1758-17612.Katranidis, A., W. Grange, R. Schlesinger, T. Choli-Papadopoulou, D. Bruggemann, M. Hegner, and G. Buldt. 2011. FEBS Lett. 585, 1859-1863