Journal
STRUCTURE
Volume 29, Issue 10, Pages 1116-+Publisher
CELL PRESS
DOI: 10.1016/j.str.2021.05.015
Keywords
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Funding
- ANR [ANR-14-CE09-0027-01, ANR-19-CE11-0020-01]
- UW-Madison Center for Interdisciplinary French Studies
- US National Science Foundation [IOS 1353674]
- Walloon Region (Belgium)
- European Regional Development Fund
- NIH [P41GM103399, S10RR02781, S10RR08438, S10RR023438, S10RR025062, S10RR029220]
- NSF [DMB-8415048, OIA-9977486, BIR-9214394]
- USDA
- Agence Nationale de la Recherche (ANR) [ANR-19-CE11-0020, ANR-14-CE09-0027] Funding Source: Agence Nationale de la Recherche (ANR)
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Researchers have deciphered the structural integration and function of a missing component in the T2SS architecture using multiple biophysical techniques, revealing the role of XcpH in bridging different subunits. They have also provided an experimentally validated three-dimensional structural model, showcasing a complete type IV filament.
The type IV filament superfamily comprises widespread membrane-associated polymers in prokaryotes. The type II secretion system (T2SS), a virulence pathway in many pathogens, belongs to this superfamily. A knowledge gap in understanding of the T2SS is the molecular role of a small pseudopilinprotein. Using multiple biophysical techniques, we have deciphered how this missing component of the Xcp T2SS architecture is structurally integrated, and thereby unlocked its function. We demonstrate that low-abundance XcpH is the adapter that bridges a trimeric initiating tip complex, XcpIJK, with a periplasmic filament of XcpG subunits. Each pseudopilin protein caps an XcpG protofilament in an overall pseudopilus compatible with dimensions of the periplasm and the outer membrane-spanning secretin through which substrates pass. Unexpectedly, to fulfill its adapter function, the XcpH N-terminal helix must be unwound, a property shared with XcpG subunits. We provide an experimentally validated three-dimensional structural model of a complete type IV filament.
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