Báo cáo Y học: The presence of a helix breaker in the hydrophobic core of signal sequences of secretory proteins prevents recognition by the signal-recognition particle in Escherichia coli

The Presence of a Helix Breaker in the Hydrophobic Core of Signal Sequences of Secretory Proteins Prevents Recognition by the Signal-Recognition Particle in Escherichia coli

Authors: Hendrik Adams, Pier A. Scotti, Hans de Cock, Joen Luirink, and Jan Tommassen

Field: Molecular Microbiology and Institute of Biomembranes, Utrecht University, The Netherlands; Department of Microbiology, Institute of Molecular Biological Sciences, Biocentrum Amsterdam, The Netherlands

Document Content:

This research investigates the role of a helix-breaking glycine residue at position –10 (Gly-10) within the hydrophobic core of the signal sequence of the Escherichia coli outer-membrane protein PhoE. The study explores how substitutions of this glycine with helix-promoting residues affect the protein’s translocation pathway. Experiments indicate that these substitutions lead to an extended α-helical structure in the signal sequence, reducing the dependency on the SecB pathway for targeting in vivo. Furthermore, in vitro cross-linking experiments demonstrate that mutant PhoE precursors with these substitutions exhibit a significantly increased affinity for P48, a component of the signal-recognition particle (SRP). This suggests that the helix breaker in cleavable signal sequences plays a crucial role in preventing SRP recognition, thereby influencing the protein’s targeting pathway alongside hydrophobicity.

Detailed Table of Contents:

• Introduction
• Materials and Methods
• Results
• Discussion
• Acknowledgements
• References