Journal of Biological Chemistry
Volume 272, Issue 35, 29 August 1997, Pages 21865-21871
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PROTEIN CHEMISTRY AND STRUCTURE
The Amino-terminal 118 Amino Acids of Escherichia coli Trigger Factor Constitute a Domain That Is Necessary and Sufficient for Binding to Ribosomes*

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Escherichia coli trigger factor has prolyl-isomerase and chaperone activities and associates with nascent polypeptide chains. Trigger factor has a binding site on ribosomes, which is a prerequisite for its efficient association with nascent chains and its proposed function as a cotranslational folding catalyst. We set out to identify the domain of trigger factor that mediates ribosome binding. Of a series of recombinant fragments, the amino-terminal fragments, TF (1–144) and TF (1–247), cofractionated with ribosomes from cell extracts and rebound to isolated ribosomesin vitro. They competed efficiently with full-length trigger factor for stoichiometric binding to a single site on the large ribosomal subunit. However, TF (1–144) and TF (1–247) differed from full-length trigger factor in that their association with ribosomes was not strengthened by the presence of nascent chains, indicating a role for carboxyl-terminal trigger factor segment in sensing the translational status. The domain responsible for ribosome binding was further investigated by limited proteolysis of recombinant fragments. A stable domain comprising the amino-terminal 118 residues was identified that was still capable of ribosome binding and thus represents a novel structural and functional element of trigger factor.

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*

Supported by the Deutsche Forschungsgemeinschaft (Bu 617/6–4), Bundesministerium für Bildung, Wissenschaft, forschung und Technologie (Project BEO 22/0311146), Fonds der Chemischen Industrie, Landesforschungschwerpunkt Baden-Württemberg, and a Boehringer Ingelheim fellowship to T.H.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Present address: Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Str. 7, D-79104 Freiburg, Germany.