期刊
NATURE MICROBIOLOGY
卷 2, 期 12, 页码 1686-1695出版社
NATURE PORTFOLIO
DOI: 10.1038/s41564-017-0041-2
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资金
- Institut Pasteur
- Centre National de la Recherche Scientifique (CNRS)
- French Agence Nationale de la Recherche [ANR-14-CE09-0004]
- European Union [294809]
- NIH [R35GM122510]
- TGIR-RMN-THC [Fr3050 CNRS]
- European Research Council (ERC) [294809] Funding Source: European Research Council (ERC)
Many Gram-negative bacteria use type 2 secretion systems (T2SSs) to secrete proteins involved in virulence and adaptation. Transport of folded proteins via T2SS nanomachines requires the assembly of inner membrane-anchored fibres called pseudopili. Although efficient pseudopilus assembly is essential for protein secretion, structure-based functional analyses are required to unravel the mechanistic link between these processes. Here, we report an atomic model for a T2SS pseudopilus from Klebsiella oxytoca, obtained by fitting the NMR structure of its calcium-bound subunit PulG into the similar to 5-angstrom-resolution cryoelectron microscopy reconstruction of assembled fibres. This structure reveals the comprehensive network of inter-subunit contacts and unexpected features, including a disordered central region of the PulG helical stem, and highly flexible C-terminal residues on the fibre surface. NMR, mutagenesis and functional analyses highlight the key role of calcium in PulG folding and stability. Fibre disassembly in the absence of calcium provides a basis for pseudopilus length control, essential for protein secretion, and supports the Archimedes screw model for the type 2 secretion mechanism.
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