Molecular mechanism and structure of Trigger Factor bound to the translating ribosome |
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Authors: | Merz Frieder Boehringer Daniel Schaffitzel Christiane Preissler Steffen Hoffmann Anja Maier Timm Rutkowska Anna Lozza Jasmin Ban Nenad Bukau Bernd Deuerling Elke |
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Institution: | 1.Zentrum für Molekulare Biologie Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Universität Heidelberg, Heidelberg, Germany;2.Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland;3.Present address: Molekulare Mikrobiologie, Universität Konstanz, 78457 Konstanz, Germany |
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Abstract: | Ribosome-associated chaperone Trigger Factor (TF) initiates folding of newly synthesized proteins in bacteria. Here, we pinpoint by site-specific crosslinking the sequence of molecular interactions of Escherichia coli TF and nascent chains during translation. Furthermore, we provide the first full-length structure of TF associated with ribosome-nascent chain complexes by using cryo-electron microscopy. In its active state, TF arches over the ribosomal exit tunnel accepting nascent chains in a protective void. The growing nascent chain initially follows a predefined path through the entire interior of TF in an unfolded conformation, and even after folding into a domain it remains accommodated inside the protective cavity of ribosome-bound TF. The adaptability to accept nascent chains of different length and folding states may explain how TF is able to assist co-translational folding of all kinds of nascent polypeptides during ongoing synthesis. Moreover, we suggest a model of how TF's chaperoning function can be coordinated with the co-translational processing and membrane targeting of nascent polypeptides by other ribosome-associated factors. |
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Keywords: | chaperone nascent chains protein folding ribosome Trigger Factor |
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