The N-terminal amphipathic region of the Escherichia coli type III secretion system protein EspD is required for membrane insertion and function

Autor: Dayal Dasanayake, Manon Richaud, Celia Caballero-Franco, Sabrina Pittroff, Juan Ausió, Michael S. Donnenberg, Armando Jardim, Ron M. Finn, Normand Cyr, Wensheng Luo
Rok vydání: 2011
Předmět:
Zdroj: Molecular Microbiology. 81:734-750
ISSN: 0950-382X
DOI: 10.1111/j.1365-2958.2011.07727.x
Popis: Summary Enterohemorrhagic Escherichia coli is a causative agent of gastrointestinal and diarrheal diseases. These pathogenic E. coli express a syringe-like protein machine, known as the type III secretion system (T3SS), used for the injection of virulence factors into the cytosol of the host epithelial cell. Breaching the epithelial plasma membrane requires formation of a translocation pore that contains the secreted protein EspD. Here we demonstrate that the N-terminal segment of EspD, encompassing residues 1–171, contains two amphipathic domains spanning residues 24–41 and 66–83, with the latter of these helices being critical for EspD function. Fluorescence and circular dichroism analysis revealed that, in solution, His6-EspD1–171 adopts a native disordered structure; however, on binding anionic small unilamellar vesicles composed of phosphatidylserine, His6-EspD1–171 undergoes a pH depended conformational change that increases the α-helix content of this protein approximately sevenfold. This change coincides with insertion of the region circumscribing Trp47 into the hydrophobic core of the lipid bilayer. On the HeLa cell plasma membrane, His6-EspD1–171 forms a homodimer that is postulated to promote EspD–EspD oligomerization and pore formation. Complementation of ΔespD null mutant bacteria with an espDΔ66–83 gene showed that this protein was secreted but non-functional.
Databáze: OpenAIRE
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