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Updated: May 1, 2026

Förster Resonance Energy Transfer Mapping: A New Methodology to Elucidate Global Structural Features
Published on: March 16, 2022
Signal recognition particle and SecA cooperate during export of secretory proteins with highly hydrophobic signal
Yufan Zhou1, Takuya Ueda2, Matthias Müller3
1Institute of Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Zellforschung, University of Freiburg, Freiburg, Germany; Faculty of Biology, University of Freiburg, Freiburg, Germany.
Abstract:
The Sec translocon of bacterial plasma membranes mediates the linear translocation of secretory proteins as well as the lateral integration of membrane proteins. Integration of many membrane proteins occurs co-translationally via the signal recognition particle (SRP)-dependent targeting of ribosome-associated nascent chains to the Sec translocon. In contrast, translocation of classical secretory proteins across the Sec translocon is a post-translational event requiring no SRP but the motor protein SecA. Secretory proteins were, however, reported to utilize SRP in addition to SecA, if the hydrophobicity of their signal sequences exceeds a certain threshold value. Here we have analyzed transport of this subgroup of secretory proteins across the Sec translocon employing an entirely defined in vitro system. We thus found SecA to be both necessary and sufficient for translocation of secretory proteins with hydrophobic signal sequences, whereas SRP and its receptor improved translocation efficiency. This SRP-mediated boost of translocation is likely due to the early capture of the hydrophobic signal sequence by SRP as revealed by site-specific photo cross-linking of ribosome nascent chain complexes.
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